AND AVES OF NORTH AMERICA. 57 



On teeth of the latter kind Emmons established his Palceosaurus carolinensis and P. 

 sulcatus; and Leidy, Compsosaurus priscus and Eurydorus serridens. On teeth of the for- 

 mer kind Emmons based his Clepsysaurus pennsylvanicus in part; bis Rhytidodon caro- 

 linensis and R. sulcatus; Leidy's Omosaurus perplexus and Lea's Centemodon sulcatus had 

 a similar origin. The names based on the lenticular teeth accompany, as prior to, or 

 synonymes of, the latter series. There is much difficulty in collating them, but 1 may 

 follow Emmons at present, in seeing in the two styles of smooth and fluted teeth, those 

 representing different species. 



In this way I have attached to the fluted toothed Rhytidodon carolinensis, Emmons, 

 the Palceeosaurus sulcatus of the same author. Emmons does not offer any grounds of 

 separation for his R. sulcatus, nor Lea his Centemodon sulcatus; neither can I find aught 

 in Leidy's Omosaurus perplexus by which it can be separated. Leidy represents it to be 

 an " Enaliosaurian," while Emmons says (North American Geology, 67-79-82), that it is 

 the same as his Clepsysaurus and Rhytidodon, citing Leidy as authority for this close ap- 

 proximation. If this be the case, the form is a shore-loving Belodont, and not nearly 

 related to the marine reptiles included under the old name of Enaliosauria. 



To the smooth toothed type belong posterior teeth named by Emmons, Palceosaurus 

 carolinensis, and by Leidy, Compsosaurus priscus and Eurydorus serridens, and anterior 

 teeth referred, erroneously in part, as I believe, to Clepsysaurus pennsylvanicus, Lea. The 

 first mentioned name cannot be used, as it has been already applied to a member of this 

 genus. The third was based on a specimen from a very remote locality, and its proper 

 application remains uncertain. The second specific name may be employed in the uncer- 

 tainty, though its describer included both fluted and smooth teeth in the same species. 



Specimens in the Academy Mus., from Montgomery Co., N. Ca., consist of vertebra?, 

 tarsal bones, etc., and parts of cranium with dermal bones of this species. A tooth in 

 place in the extremity of the ramus of the mandible, is as smooth as those from more pos- 

 terior positions in the jaw, figured by Emmons, N. Am. Geol., p. 69, fig. 42, which in 

 some measure supports Emmons' hypothesis of the uniformity of the characters of the sur- 

 face sculpture. The cranial fragments indicate a Belodont, and the vertebra? are different 

 from those of Clepsysaurus. 



The vertebra?, (No. 5) from the coal of Chatham Co., N. Ca., were accompanied by 

 teeth of the fluted character, though they were not on the same block. As the former 

 indicate a species distinct from that from Montgomery Co., 1 have regarded them as pro- 

 bably pertaining to Emmons' Rhytidodon carolinensis. 



The remains, (No. 6) from Phcenixville, include vertebra?, bones of the pelvic arch and 

 posterior limb, with dermal bones, but no teeth. They indicate an animal distinct from 

 either of the preceding. 



AMEEI. PHILOSO. SOC VOL. XIV. 15 



