4i0 THIRD REPORT — 1833. 



Dr. Adam observes, that by the completion of Mr. Clift's 

 labours in adapting and mounting the remains of this animal, 

 some peculiarities now visible in the internal structure of the 

 bones will be concealed, and on this account he directs the 

 attention of zoologists to the following observations : 



"In the thicker parts of the ribs as well as of the bones of 

 the limbs wliere broken, there are dispersed and conglomerated 

 in the reticulated texture, like the spherules in some crypto- 

 gamous plants, numerous round bodies from one tenth to two 

 tenths of an inch in diameter. These bodies are hard, but of 

 a steatomatous appearance: they seem to have resulted from 

 tlie same exuberance of ossification so conspicuous in the ex- 

 ternal surface. The external surface of the thicker parts of 

 the bones looks as if formed by a conflict of the osseous spi- 

 culae, which are of the size of coarse needles." 



Dr. Adam is of opinion, that probably the nails of the me- 

 gatherium might have been doubled under the foot in the same 

 manner as those of a living cognate species, the short-tailed 

 manis, the feet of which living species had hitherto been incor- 

 rectly figured in zoological works. 



On some new Species of Fossil Saurians found in Atnerica. 

 By R. Harlan, M.D., of Philadelphia. 



The species of saurians mentioned in this communication 

 had been all examined by Dr. Hai'lan, and a full account of 

 them is preparing for publication. The following extracts will 

 make known the names and localities of these fossils. 



1. Ichthyosaurus Missouriensis. — A fragment of the head 

 has been found in a hard bluish grey limestone, near the junc- 

 tion of the Yellow-stone and Missouri rivers. 



2. A dorsal vertebra, analogous to those of plesiosaurus, 

 except that its length is remarkably greater in proportion to its 

 breadth. Found in marl on the banks of the Arkansaw river : 

 supposed to belong to a very large individual. The marl con- 

 tains many bivalve shells. 



Remains of crocodiles, geosauri, &c., were also mentioned 

 by Dr. Harlan as occurring in West New Jersey in marls. 



Remarks on Genera and Subgenera, and on the Principles on 

 inhich they should be established. By the Rev. Leonard 

 Jenyns, A.m., F.L.S. 



The object of this paper was to make some remarks on the 

 great multiplication of genera at the present day, and to show 



