On inspecting the mouth I observed two rows of teeth situated on the margin of each jaw, one internal to the other, the outer row being larger and stronger than the inner; and it is probable that the inner row is intended, as in the shark, to replace the front row, when lost from time or accident. On the palate were also placed two rows of very fine teeth, and the other parts of the mouth were rough. I made several dried preparations of the head of this fish, which well displayed the form of the disk; and, by keeping the mouth distended, the rows of teeth could be distinctly seen and examined. The fins are, two pectoral, two ventral, one dorsal, and one anal; the whole of which are of small size, in proportion to the body of the fish, as well as the tail. The disproportion of the size of the head, and the diminutive size of the fins and tail, must consequently prevent its swimming to any distance, for when swimming its motion is very tardy, and apparently laborious. Nature has, therefore, provided it with a means of attaching itself to rocks, the bottoms of ships, &c. I have seen them attached more commonly to the body of the _Squalus carcharias_, or white shark, than to any other species: whether it is that this species of shark is the most usually met with, I cannot determine; but on a blue shark, although accompanied by pilot-fish, I never, in the few instances I have met with, saw a Remora attached, although, in the other species, I have always seen some attached: if this, on further observation, is found to be the fact, it may be probably accounted for by the _Squalus carcharias_ more frequently approaching the land. The sucking-fish not being able to swim any distance, must generally remain attached to rocks, &c., and from them removes itself to the shark as he approaches. The sucking-plate enables these fish to change their locality, by attaching themselves to the stronger inhabitants of the deep, and precludes, as on the rocks, the danger of their being driven by tempests remote from their usual food and rest. This fish is also destitute of an air-bladder. The Remora was supposed, by the ancients, to have the power of arresting the progress of a ship under full sail; and, by others, their nourishment was supposed to be derived from the body of the shark, or from any substance to which it adhered: all these chimeras have, however, been long since dispersed. Their food has been found (from the examination of the contents of the stomachs of the specimens captured) to be minute marine insects, &c.