superior connections of the vomer in the horse are peculiar, inasmuch as the inferior surface of the leaflets of the ethmoid, instead of lying in contact, as is usual, with the ethmo-vomerine lamina for a considerable extent, is completely floored in by the upper part of the palate bone, which is expanded for that purpose. Even in the horse, however, a slender lamina, immediately in front of the palate bone, and in contact with its nasal foramen, passes downwards and inwards on each side from the framework of the ethmoidal turbinations to the margin of the vomer; but the vomer and it are not anchylosed until other sutures also have begun to be obliterated.

The vomer in the rodentia is remarkable in having very little tendency to come in contact with the superior maxillaries. As far as I have observed, it is always continuous with the lateral masses of the ethmoid.

In the skull of the rabbit there is only one great anterior palatine foramen; for, although the mesial processes of the intermaxillaries project well backwards, the palate plates of the superior maxillaries do not come far enough forwards to meet them. The vomer does not at all approach the superior maxillaries; its posterior margin terminates inferiorly in a thickened angle, which articulates with the intermaxillaries in such a manner as to make their inferior aspect continuous with the posterior margin of the vomer. In front of this, the lamina bounding its groove are prolonged on the upper surface of the intermaxillaries, as we have seen in other animals (fig. 4).

In the porcupine and squirrel the vomer is not in contact with the superior maxillary bones; in the rat and the beaver it is.

In the quadrumana the mesial process of the intermaxillaries is so slightly developed that the anterior extremity of the vomer frequently falls short of it by a slight interval. In monkeys the vomer and orbital plates of the ethmoid are continuous; but in the skull of a young Chimpanzee in the University Museum, the arch of bone which unites them is separated at one extremity from the ethmoid by a suture, and at the other only touches the vomer. This piece of bone has all the essential characters of the sphenoidal spongy bones of the human subject.

The vomer and sphenoidal spongy bones in man.-Having found the vomer and lateral masses of the ethmoid so universally connected, we naturally inquire how they are related in man. They are not in contact. Their only connection is that the expanded portion of the vomer which grasps the rostrum lies beneath the sphenoidal spongy bones, and that these articulate with the lateral masses of the ethmoid. Now, seeing that the sphenoidal spongy bones are recognised as ossifications distinct from the sphenoid, I think we have already sufficient evidence to prove that they represent the ethmo-vomerine laminæ, by aid of what we have noticed in the Chimpanzee's skull; for it is impossible to doubt either that the distinct bone which lies between the orbital plates of the ethmoid and the vomer in that skull corresponds to the ethmo-vomerine lamina of other monkeys; or, on the other hand, that it corresponds to the sphenoidal spongy bone in man. But the correspondence becomes much more distinct. when we study the early condition of the sphenoidal spongy bones. The most interesting condition of these bones is when, in the skulls of young children, they can be got completely ossified and not yet destroyed by amalgamation with the neighbouring bones. In this state the sphenoidal spongy bone is somewhat of the shape of a hollow pyramid with the apex directed backwards, its inner aspect parallel to its fellow, and its cavity (the first form of the sphenoidal sinus) opening at its base into the nasal cavity in front (fig. 2). This pyramid is constructed by the union of at least three distinct pieces of bone. Firstly, there is an orbital piece, forming a portion of the wall of the orbit between the ethmoid and sphenoid, an element, I believe, in the formation of the orbital wall not hitherto observed. It articulates with the orbital process of the palate bone, and, together with the inferior piece, completes the nasal foramen of the palate-bone, namely, the foramen called spheno-palatine, but which we have seen to be invariably ethmo-palatine in other animals. The superior piece bounds the sphenoidal sinus above and on the inside, and ultimately becomes incorporated with the sphenoid bone. The inferior piece is the largest of the three; it forms the floor of the sphenoidal sinus, and the under half of its opening

in front, and includes the greater part of what has hitherto been recognised, and described under the various names, sphenoidal spongy bone, sphenoidal cornu, and bone of Bertin. Its inner margin is joined by the superior piece at an acute angle, and is prolonged downwards and forwards so as to lie edge to edge with the corresponding lamina of the vomer, immediately in front of the thick dilated part of that bone. Beneath and behind is the sphenoidal process of the palatebone, and behind that is the internal pterygoid process. In man, therefore, as in other mammalia, we find three processes in succession from behind forwards, viz., the pterygoid bone, the sphenoidal process of the palate-bone, and an arch passing from the ethmoid to the vomer, adapted to it edge to edge; and moreover, this arch completes the foramen which divides the ascending part of the palate-bone. It in every respect, therefore, corresponds with the ethmo-vomerine lamina. The reason why the arch formed by the vomer and ethmoid is broken up in the human subject into so many separate pieces is to be sought in the characteristic peculiarities of the human subject, particularly in the very slight development of the organ of smell, and the rapid curvature of the cranio-facial arch. But on this subject I hope to speak more fully on some future opportunity. The inferior edges of the sphenoidal spongy bones, which in childhood lie edge to edge with the vomer, are in the adult state smoothed down to a mere ridge, and considerably separated from the middle line by the expansion of the sphenoidal sinuses.

We have now seen that the relations of the vomer to the lateral masses of the ethmoid in the human subject are essentially the same as in the mammalia generally. In early life the human vomer resembles those of other mammals in form likewise, and seems to be connected in the same manner with the intermaxillary bones. In the skulls of foetuses and young children the vomer mainly consists of two lamina extending upwards on the sides of the cartilaginous septum of the nose. The inferior edge exhibits a flat surface with a raphe in the middle line, which articulates with the superior maxillaries proper, i. e., with the part behind the anterior palatine foramen; and which narrows to an edge behind, where it comes in contact with the palate

bones. But this surface ceases abruptly in front, and only the lamina bounding the groove for the cartilage is prolonged on the intermaxillary part of the palate (fig. 3). In the adult state both the scooped projection lying on the intermaxillaries, and the remains of the surface for articulation with the superior maxillaries, can be seen, when the vomer still admits of being accurately disarticulated. But this is not often, as it soon becomes anchylosed with the neighbouring bones; and even when this has not happened, it requires that portions of the other bones be sacrificed for the sake of removing it entire. As the face elongates, the upper part of the vomer undergoes much alteration; not only is there a considerable development of lamina in the mesial plane beneath the groove, but usually the lamina bounding the groove deviate from the mesial line, and one of them becomes more developed than the other, and is more extensively anchylosed with the central plate of the ethmoid, which, growing downwards, replaces the cartilage between them. In consequence of these changes taking place at a comparatively early period, the specimens which are sold with disarticulated skulls, and from which the descriptions in text-books are drawn up, are seldom complete, and have most frequently more or less of the central plate of the ethmoid adherent to them. Thus the vomer is described as exhibiting at its upper and back part a cul-de-sac for the rostrum. Such a cul-de-sac is often seen, but the central plate of the ethmoid invariably enters into its formation, for it is only the ethmoid, and never the vomer in the slightest degree, which replaces the cartilaginous septum.

Explanation of Plate V.

Fig. 1. The vomer and lateral masses of the ethmoid of a lamb, seen from below. a, The inferior margin of the vomer, rough posteriorly, for articulation with the maxillaries, and smooth in front, where it comes in contact with the intermaxillaries; bb, the grooves which complete the nasal foraminæ of the palate bones. The spaces between the grooves and the margins of the vomer represent the ethmo-vomerine laminæ, and on the outer aspects of the grooves are the small orbital surfaces of the ethmoid.

Fig. 2. The vomer, ethmoid, sphenoidal spongy bones, and left palate and maxillary bones, from the skull of an infant; seen from behind (slightly enlarged). a, Orbital plate of the ethmoid; b, posterior extremity of the vomer; e, sphenoidal process of the palate bone; d, orbital surface of the palate bone, and immediately above it is the orbital portion of the sphenoidal spongy

VOL. II.

N

bone. Between the two processes of the palate bone is the spheno-palatine foramen, completed above by the inferior portion of the sphenoidal spongy bone. e, The superior portion of the sphenoidal spongy bone.

Fig. 3. Another view taken from the same specimen: a, b, c, The parts of the inferior margin of the vomer for articulation with the palate, maxillary, and intermaxillary bones respectively; d, inferior aspect of the sphenoidal spongy bone; e, orbital plate of the ethmoid seen in perspective; f, inferior turbinated process of the ethmoid.

Fig. 4. Illustrates the articulations of the vomer in the rabbit, Above are the vomer and ethmoid forming one bone. Beneath are the bones of the upper jaw of the left side, and a portion of the intermaxillary bone of the right side adhering to it. a, Anterior extremity of the vomer, grooved for the cartilaginous septum of the nose; b, the part of the vomer which articulates with c, the extremity of the expanded mesial processes of the intermaxillary bones, forming turbinations in connection with Jacobson's organ.

VI. On the Discovery of Nullipores (Calcareous plants) and Sponges in the Boulder Clay of Caithness, By CHARLES W. PEACH, Esq., Wick. (Specimens were exhibited.)

In a paper read to the Society in March 1855, "On the Calcareous Zoophytes of the Boulder Clay of Caithness," I intimated that, at a future time, it was my intention to give you one on the flora of that formation. I have delayed from time to time, that I might search in wide localities, and thus have succeeded in procuring several specimens at Wick, and the burns of Haster and Freswick.* Mr Cleghorn has also found specimens at Wick, and Mr Dick in and around Thurso. Although pretty widely distributed in the country, nowhere is it found in abundance. At times it is quite soft when first taken out of the clay; it hardens on exposure, and cracks in the drying, and then, should an attempt be made to make a section, it crumbles to pieces. In one taken from the clay on the side of Wick harbour I got a pretty good slice, and have made out under the microscope the cellular structure; it agrees with that of the Melobesia polymorpha of Harvey, as may be seen by the specimen herewith sent, mounted in Canada balsam, and a specimen on stone, also from Wick. In one speeimen, I noticed, as well as the spreading base, the papillary eminences peculiar to this species; and in another the indentations made by saxicavous creatures. When passing Freswick

Since this paper was read I got, on the 18th May (Queen's Birth-day) 1860), splendid specimens in the Burn of Strath, near Watten.