intimately allied to the tortoise ; and decidedly connect it with the Saurian order.
It will be necessary to subjoin a few words on the inferior hatchet-shaped processes which may be seen depending on either side from the lower part of the cervical vertebrae. Most animals present traces of these processes; they are particularly prominent in many of the long-necked quadrupeds, and in birds project into a long styloid branch : a rudiment of these may be observed in man, but I am not aware that any particular name has been assigned to them*. They have been sometimes confounded with the transverse processes, to which they often form a wing-like appendage. These processes are important, as serving to determine the number of the cervical vertebra:, and as affording very close analogies between the plesiosaurus and the crocodile ; in both these animals these inferior hatchet-shaped processes are exactly similar in figure, and form separate pieces attached to the body of the vertebræ by a double stem : in the figures given of the cervical vertebra* in my former memoir, this stem alone and the double suture which receives it, could, from the imperfect state of the specimens, be represented ; but I then expressed my conviction that the structure resembled that of the same part in the crocodile, and my conjecture is now verified.
The thirty-five anterior vertebra; of the plesiosaurus exhibit these processes distinctly characterized, and are therefore beyond all doubt cervical ; in the six following the processes become lengthened, and gradually lose their hatchet-shaped extremity, assuming rather the form of false ribs, and should therefore perhaps be classed as anterior dorsal ; but the whole forty-one are clearly placed before the pectoral extremities. In the crocodile there are seven cervical vertebra with hatchet-shaped processes, and three anterior dorsal with false ribs before the humero-sternal portion.
Since flexibility must evidently be the end of this great multiplication of the joints, it may perhaps excite surprise that the joints, instead of articulating as in birds by cylindrical surfaces, should have their contiguous faces nearly flat, which must have allowed a less freedom of motion between each vertebra : but it may be answered, that the increased number of the joints compensated for the stiffness of each.
Dorsal Vertebræ.-I have nothing to add to my former remarks on this part of the column : the greater part of these, in the splendid specimen from Lyme,