teeth are then taken with the hair, drawn out of the skin of the fish, and move softly and harmlessly along.

The above, I imagine to be the sole purpose of these plates. The sucker is quite sufficient for the mere purposes of adhesion; and may be probably used without the teeth or plates, when the remora fixes itself upon rocks or stationary objects; but the plates and teeth are required to enable it to fix itself upon bodies in rapid motion. A necessary consequence of my view (if correct) is, that the remora must always fix itself with its head in the same direction as the fish or vessel it attaches itself to, is going; it can never be found with its head to the tail, for the only way by which it could fix itself, if placed in that position, would be by either it or its supporter swimming backwards, which they cannot easily do. I do not know how the actual fact stands in regard to this position of the fish, and invite observers to notice it in future; but I feel sure that it is an impossibility for a remora to fix itself with its head pointing towards the tail of its supporter. And its being so is only another instance of the beautiful harmony and adaptation of things which are daily forced upon our attention. It would have been as easy to have made the plates and teeth point forwards as backwards, and then the remora would only have had to meet its supporter, and fix itself in brushing past him; in that case, it would have always been looking towards the tail, which would have entailed more serious inconveniences than at first sight appear. In the first place, the rapid motion of the creature to which it has attached itself through the water could not be met by the tail of the remora in a straight position; it would always be bent aside, which would not be comfortable. Again, if the remora opened its gill-covers to breathe, the rush of water would fill them, and keep them open, so that in a short time it would be drowned. Instead also of meeting its food and snapping it as it came, it would be like Tantalus, and never see it till it was borne resistlessly away from it. And supposing it to escape all these dilemmas, and, heartily sick of its position, to have resolved to lead a life of independence and self-reliance henceforward, how was it to escape from the false position it had assumed? Instead of easily escaping by moving forward (as the real remora does), our inverted animal would only fix it

self the more firmly the more it attempted to escape. The only release would be by swimming backwards, but it would find it as difficult to do so against the onward impulse of the larger fish, as we ourselves too often find it to retrace a false step.

The mention of their food suggests to me that the curious conformation of the teeth, which I have above described, may help us to a knowledge also of this subject; for that is a point which is not as yet quite certain. Sir Wm. Jardine, in the Naturalist's Library, says it feeds on small fishes. The usual belief of sailors is, that it feeds on the fragments of the prey of the shark. Commerson thought this likely enough; but Lacepede mentions that in some seas they are in great numbers, and that they follow vessels in shoals in order to feed on the animal matter thrown away. This, he says, has been particularly noticed in the Gulf of Guinea, and that is the reason, according to Barbot, that the Dutch who frequent the west coast of Africa have called the remora "poisson d'ordure."

The teeth, I think, show that this is very probable. The mouth is wide, with the lower jaw very much projecting beyond the upper, which, as it were, fits into the cavity of the mouth, just within the teeth of the lower jaw. The lower jaw has several rows of small sharp teeth, curved inwards; but the upper jaw alone has the peculiar outer fringe of close-packed regular pedunculated teeth already described. These are apparently admirably adapted to serve the purpose of a sieve. Suppose the small sharp curved teeth in the lower jaw, along with the inner irregular row in the upper jaw, to seize a portion of comminuted matter, and the mouth to be then closed, the water would escape out at the intervals between the peduncles of the upper fringe, and the food be retained within. The small size of the seizing teeth, and the several rows of still smaller ones, show that they are not adapted for seizing any solid very coherent body. It must be something that it requires a great many points of contact to lay hold of, and which is probably in a soft semifluid state. The thick velvet-like pavement of minute teeth in the interior of the mouth is obviously constructed for comminuting some substance which has been very much comminuted already, and the apparatus on the branchial rays

would appear to be intended not only for comminuting purposes, but also (or perhaps rather) for the same purpose as the outer fringe of teeth in the upper jaw-viz., to prevent the escape of the food with the water through the gills.

It has been a subject of conjecture how the Echeneis can play before and around and close to the very jaws of the shark without being devoured. Some have supposed that these terrible fishes have a sort of antipathy to the taste or smell of the flesh of the remora, and hence do not care to eat them. We certainly have plenty of instances of animals instinctively refusing to feed upon what is bad for them. Others fancy that the remora has sufficient agility, address, or cunning, to escape the murderous teeth of the shark; or, again, it may not be an unreasonable speculation, that the shark might find the remora stick in its throat in swallowing it, and after one or two trials abstain from them.

In examining some specimens of E. remora, which were kindly lent to me by my friend Dr Fleming, I was struck by finding one receiving strict poetical justice from the intrusion. of a Lernean sticking to its head, which I have no doubt gave it as much uneasiness as ever the remora itself occasioned to any fish to which it may have chosen to affix itself. The position which these parasites occupied will be seen in fig. 4, where the head of the remora is figured with them attached to it.

There were six or seven of them in a greater or less stage of

advancement-one or two only a couple of lines in length, and two of them nearly an inch, and buried at least as deep in the head of the fish. All these, with the exception of one, had merely the appearance of threads hanging out from under the edge of the disk. One, however, emerged from the side of the mesial line nearly in the centre of the disk. They all entered the head at some chink or cranny, where the young crustacean had found a hiding place. The individual that occupied a position on the disk itself was thinner, and had less substance than the others; from which we may infer, that although it had been able to live and grow in an occasional vacuum, it was not altogether insensible to the injurious effects of such treatment.

They were all annular, of a dirty olive colour (the same as the colour of the fish), and semi-transparent. At the termination of one of them, I made out, by a little pressure under the microscope, that there were two nipples or slight elevations, which were probably, as was suggested to me by Professor Owen, the points of attachment of the two ovaries which had dropped off. These traces of ovaries were found on one of the thread-like individuals; and this would seem to imply that it was fully grown, although the great difference of form in another specimen, which I am going to describe, shows that if full grown, it was at least not fully developed. The one I refer to was a somewhat larger specimen than any of the rest, of the form and with the appendages shown in fig. 5. This shows that it is a species of the genus Penella, one of the Lerneans which has appendages at its termination like the wing of an arrow. This specimen had very much the appearance of a miniature arrow with a well-feathered shaft sticking in the flesh. Seen sideways, the feathers are found to be buds arranged in a double or treble oblique row, as represented in the sketch on the right hand, which is a magnified outline, intended to show the position and arrangement

Fig. 5.

of the buds when looked at in profile. The left hand sketch is a representation of it as seen in front; the middle sketch is the same, but more highly magnified.

Milne Edwards divides the genus Penella into two sections, one distinguished by the head (which penetrates deep into the victim, burrowing through flesh or bone indifferently, and generally attacking some part of the head) being furnished by two horns or diverging prolongations; the other by having three such arms or horns on its head.

Two species of each section have been described. The Penella sagitta, Lin., and P. filosa, Lin., fall under the former section, and the P. Blainvillei and P. Sultana, Nord., under the latter. The present species corresponds with none of these. I have endeavoured to dissect out one or two of them to find to which section it belonged, but their minute size, fragile texture, and great length to which it was buried in the head, combined with the degradation of the tissues, owing to their having been long immersed in spirits, have got the better of me. I am, therefore, obliged to confine myself to the above external description of the portion of the creature which I saw. From its habitat, I have named it Penella

remoræ.

On the Discovery of Paradoxides in the altered Rocks of Eastern Massachusetts. By Professor WILLIAM B. RoGERS, F.G.S., &c.

It is well known that the altered slates and gritty rocks which show themselves interruptedly throughout a good part of Eastern Massachusetts, have, with the exception of the coal measures on the confines of this state and Rhode Island, failed hitherto to furnish geologists with any fossil evidences of a Palæozoic age, although, from aspect and position, they have been conjecturally classed with the system of rocks belonging to that period. Indeed, the highly metamorphic condition of these beds generally, traceable, no doubt, to the great masses of igneous material by which they are traversed or inclosed, would naturally forbid the expectation of finding in them any distinguishable fossil forms.