sembling so closely, in that state, the larva of the common Cheimatobia brumata, as to be almost undistinguishable.

II. Remarks on some Comparative Anatomical Distinctions between the Skull of the Manátus Senegalensis and that of a Manatee from the Bay of Honduras. By JAMES M'BAIN, M.D., R.N. (Specimens exhibited.)

The skull of a Manatee from the Bay of Honduras, which I now exhibit to the Royal Physical Society, was presented to the Hunterian Museum of Glasgow about seventeen years ago, along with a considerable portion of the skeleton, by Mr James Banks, late of Belize, Honduras, but latterly residing at Prestonpans.*

In the remarks which I shall have occasion to make on this skull, it will be necessary to refer to the "Notice of a Skull of a Manatee from Old Calabar," which I read at a meeting of the British Association at Aberdeen in September 1859, and which was published in the Proceedings for that year.

In the skull from Old Calabar, which I have brought here for comparison, the occipital bone, petro-mastoid, and tympanic bulla, are wanting; and in the skull from the Bay of Honduras there is a transverse section at the base of about an inch in breadth, extending across between the tympanic bones, which involves the loss of nearly the whole basioccipital. It is in this lost part that several of the principal foramina at the base of the skull are situated.

That portion of the crista interna formed by the inner tables of the frontal bone, extending upwards and backwards from the largely developed crista galli of the ethmoid in the skull from Old Calabar, is almost wanting in the skull from Honduras. The parietal part of the crista interna in the latter skull is well-marked, increasing in size backwards until it expands into a large internal occipital protuberance, with a broad transverse ridge which separates the cerebrum from the cerebellum. The palate of the skull from Honduras, measured from the incisive edge of the premaxillary bones to the posterior part of the spinous cleft of

* I regret to see a notice of Mr Banks's death in the "North British Advertiser,” as having occurred at Prestonpans on the 6th instant.

the palate bone, is 8 inches; from this point of the palate bone to the posterior edge of the basi-sphenoid, the distance is 2 inches; the length from the incisive edge of the premaxillaries to the coalesced basi-sphenoid and basi-occipital is, therefore, 11 inches, or half an inch less than in the skull from Old Calabar; and from the anterior border of the premaxillary bones to the anterior edge of the foramen magnum, the total length at the base of the Honduras skull is 13 inches. The pterygoid bones are 2 inches in length, with a smooth outer ridge behind, and another inner ridge, which terminates in a short obtuse hamular process. They coalesce with the pterygoid processes of the palate bone, which are large, twisted backwards and outwards, and cover, without concealing, the posterior aveoli.

The foramen magnum is oval transversely, 2 inches from side to side, and an inch and a half from above downwards. The occipital condyles are 18th inch in length, and 16th inch in breadth, and approximate to each other in front. The paroccipital wings at the posterior roots of the condyles expand upwards, inwards, and outwards, in a broad semilunar form, convex above and concave below, where they join the less prominently developed mastoids.

From the posterior edge of the foramen magnum, along the perpendicular occipital spine, to the large straight transverse occipital ridge, the distance is 2th inches; and from the middle of the occipital crest to the anterior incisive margin of the premaxillary bones, following the curve of the coronal aspect, the length of the skull is 15 inches. There is a deep hollow space extending along the middle of the upper convex aspect of the skull, which is formed by a strongly developed longitudinal ridge on each side. These lateral ridges commence at the posterior inferior parietal angle, where they are 3 inches apart; the parietal portion of the ridges gradually approximate as they advance forwards, until, at the coronal suture, they are only an inch apart. The ridges again diverge, increase in size, and form two anterior superior parietal processes, which extend forwards for about 2 inches in a notch in the frontal bone. They then advance forwards and outwards as frontal ridges, nar

row at first where they bound the upper part of the temporal fossæ, but gradually spread out into thick, broad, triangular-shaped orbital plates, convex above and concave beneath, to form the roof of the orbital chambers. These orbital plates are larger than in the African skull. The premaxillary bones are 7 inches in length, and extend backwards at the inner edge of the orbital plates of the frontal bone for about 2 inches in the skull from Old Calabar; the premaxillaries are much smaller, less deflected in front, and terminate behind at the anterior part of the frontal bone. The distance from the incisive edge of the premaxillaries to the fore part of the orbital cavities is 5 inches, or an inch less than in the African skull. The orbital cavities are larger and more rounded in the Honduras skull than in that from Old Calabar. The length of the zygomatic process is 5 inches, or half an inch less than in the African skull; it is also much less massive, more curved and concave below. The glenoid surface is more elevated, with two deep depressions at the under and back part, which are but very slightly marked in the African skull. The malar bone is 6 inches in length, and extends from the outer edge of the glenoid ridge to the anterior part of the orbit. It has a narrow zygomatic process behind, which gradually expands into a broad vertical maxillary process, which terminates in a twisted curved horizontal orbital plate, to form the outer part of the floor of the orbital cavity; and this orbital plate rests on a similar curved orbital process of the superior maxillary bone. The inner part of the floor of the orbits is formed by a bridge-like process of the orbital plates of the superior maxillary bones, which extends outwards from the alveolar processes of the upper jaw. There is a large infra orbital foramen, about an inch in diameter, opening directly in front. The anterior nasal aperture is considerably larger in the American than in the African skull, although the extreme length and breadth of both is almost the same. In the African skull the aperture is contracted from side to side, both before and behind; and as the nasal fossa is narrower, shallower, and altogether less capacious, the size of the anterior nasal aperture appears

less than it really is. The frontal and premaxillary bones, as already described, are much larger in the American than in the African skull; and as the parts of these bones which form the boundary of the anterior nasal aperture are also broader, thicker, and more expanded from side to side, there is a corresponding difference in form and size of the anterior nasal aperture in the two skulls. The posterior nasal aperture is somewhat less in the American skull.

The left bulla tympani is present, but without any opening; it is of an oval shape, keeled beneath, an inch and a half in length, an inch broad, and rather more than half an inch in thickness. It is attached in front by a short twisted process to the anterior portion of the pars petrosa, and by another larger transverse process behind. There is a deep oval depression at the upper and back part, a third of which is open above and a little in front, the roof being formed by the under concave surface of the anterior process of the petrous bone, which is lodged in a deep cavity at the under and back part of the root of the zygomatic arch. The pars petrosa and the posterior process occupy another depression, formed partly by the root of the zygomatic process and partly by the mastoid bone. The posterior process of the pars petrosa slightly projects externally by a transverse opening more than an inch in length, and half an inch from above downwards, situated between the occipital and mastoid bones, corresponding to the position of the foramen mastoideum. The anterior and posterior processes of the petrous bone, which are quite distinct in the Baleen cetacea, are so compressed together with the petrous part in this skull, as to appear to form but a single bone, about 2 inches in length, and rather less in breadth.

The lower jaw is less massive than that of the African skull. Its length on each side, from the incisive edge to the angle of the jaw, is 7 inches, and the depth about 2 inches. The perpendicular height from the angle to the condyle is 5th inches, and the posterior part of the rami curves upwards from the angle towards the root of the condyle, but is nearly straight in the African skull. The distance from the condyle to the anterior point of the co

ronoid process is nearly 4 inches, the upper border of the coronoid process rising two-thirds of an inch higher than the condyle. The maxillary canal greatly exceeds in size that in the African skull, and is not separated from the inflated extremity of the alveolar process posteriorly. It terminates in front in a wide-grooved foramen menti, with another foramen behind, which communicates with the maxillary canal, and is equal in size to the true foramen menti in the African skull. The distance from the angle of the lower jaw to the symphysis menti is about 4 inches, and the angle of the jaw is but slightly inflected, whilst in the African skull there is an acute inflected angle, the two inner points of the angles being only 3th inches apart. In the lower jaw of the skull from Honduras, the distance between the two inner points of the angles is 4,3th inches.

The alveolar process of the lower jaw is 5 inches in length, slightly curved outwards and upwards at the posterior termination, where it perforates the roof of the coronoid process, and protrudes by its inflated extremity into the maxillary foramen.

There are eight molar teeth on the left side of the lower jaw, and an empty socket in front; each tooth has two large transverse bi-tuberculated ridges, and a smaller ridge behind, implanted by two roots in sockets about an inch deep, like those in the lower jaw of the African skull. The roots of the teeth are flattened transversely, corresponding to the transverse coronal ridges, and the posterior root is bifurcate at the apex.

The molar teeth in the upper jaw have two transverse trituberculated ridges, with a ridge-like thickening at the cervix anteriorly and posteriorly, similar to, but less in size than those in the African skull. Each molar tooth in the upper jaw has three roots, the inner root compressed longitudinally, the two outer roots compressed transversely; but the roots of the teeth are less divergent, and the external anterior root is less curved backwards, than those in the African skull. The three posterior teeth on each side of each jaw are nidamental; the three succeeding teeth are but very slightly worn; whilst those in front, still in situ, have their