180 Prof. R. Owen on rare Extinct Vertebrates. 



in the Yale Museum show conclusively that the dentigevous 

 bones of the palate in various genera of Mosasauroids were 

 attached posteriorly to the tympanies and to the pterapophyses 

 by ligament, to the mamillaries by the medium of the ecto- 

 pterygoids, and to the true palatines by suture. " Cope has 

 called these dentigerous bones ' palatines,' and has stated that 

 they were separated from the quadrates by intervening bones* ; 

 but on both points he was in error. The true palatines are 

 small edentulous bones in front and outside of the ptery- 

 goids " f. 



In regard to the vertebrae in Mosasauroids, the rich collec- 

 tion in " Yale Museum " does not appear to affect or add to 

 the characters of the several divisions of the backbone, as 

 defined by Cuvier and his successors, and as summarized in 

 the 'Annals' for July 1879, p. 57, pi. viii. The best-pre- 

 served specimen of the vertebral column appears to be of an 

 individual of the proportionally shortest form of Mosasauroid 

 (Holosaurus abruptus, Marsh) . This skeleton shows 98 ver- 

 tebra? ; but the tail is incomplete, and the preserved caudals 

 are of the tenth type in the above " summary." 



"With the important additions to a knowledge of the frame- 

 work of the pectoral arch and its appendages, Prof. Marsh has 

 materials for the restoration of the bones of the fore fin in 

 both Edestosaurus (PI. VIII. fig. 1) and Lestosaurus (fig. 2). 

 Neither of these genera supports the restoration figured by Prof. 

 Snow in the Leiodon of the Kansas chalk \. They correspond 

 more closely with that of a Lestosaur described and figured 

 by Marsh in the ' American Journal of Science and Arts ' for 

 June 1872 §. The digital formula in Edestosaurus dispar is 

 I. 3, II. 5, in. 5, IV. 4, v. 3 (PI. VIII. fig. t)\\. The same 

 formula is repeated in the pectoral fin of Lestosaurus simus *\. 

 The fin is relatively broader in Edestosaurus ; and in the spe- 

 cimen figured of E. dispar seven carpal bones (four in the 

 proximal, three in the distal row) intervene between the five 

 metacarpals and the two antibrachial bones. In the figured 

 specimen of Lestosaurus (PI. VIII. fig. 2) two carpals are 

 shown at the ulnar end of the distal row, and the same 

 number at the same part of the proximal row. 



With regard to the antibrachial bones, I may observe that 

 in the Orocodilia**, the Lacertiliaftj the Chelonia Jf, and the 



* ' Vertebrata of the Cretaceous/ p. 118. t Marsh, he. cit. p. 86. 



X Copied in plate viii. tig. 13, of Ann. & Mag. Nat. Hist, for July 1879. 



§ See also Owen "On the Affinities of the Mosasauridse, as exemplified 

 by the Bony Structure of the Fore Fin," Quart. Journ. Geol. Soc, August 

 1878. 



|| Marsh, he. cit. pi. i. fig. 1. H Ibid. fig. 2. 



** Cuvier, Ossem. Foss. 4to, t. v. 2 e partie, p. Ill, pi. iv. fig. 13. 



tt Ibid. pi. xvii. fig. 45. XX Ibid- pi. xii. figs. 11-15. 



