320 KANSAS UNIVERSITY SCIENCE BULLETIN. 



"conical epiphyses" which penetrate into a cylindrical sheath 

 "so as to meet, or nearly meet, in the center." The turtles 

 and plesiosaurs both have a very peculiar scapula. In both 

 groups it is fundamentally biradiate, and it has been claimed 

 that this condition of the scapula is due to the fusion of the 

 procoracoid to the true scapula in both groups and the homol- 

 ogous mode of formation of this element was made the basis 

 for relationship. Further relationship has been claimed on the 

 fact that the broad character of the pectoral and pelvic girdles 

 of the plesiosaurs resembles to some extent the plastron of the 

 turtles, and there has been some attempt to correlate the ele- 

 ments in the two groups. There is, also, an undoubted simi- 

 larity in the manner of life of the two groups, and this has 

 been a claim to affinity. 



The question of the relationship of the turtles and plesio- 

 saurs has been discussed by various authors, notably Seeley, 

 Hulke, Baur and Williston. An impetus toward the final con- 

 clusion of the matter has been given by the recent studies of 

 Williston on the skull of Brachauchenius, and by the author's 

 studies on reptilian epiphyses.- 



The first basis of relationship to be discussed is that of the 

 number of segments in the neck and tail of turtle embryos, 

 first brought forward by Parker."^ He says (p. 50) : "One of 

 the most remarkable things in the embryo (of the green turtle) 

 is the large number of somatomes, in the neck especially, and 

 also in the tail, as compared with what is seen in the inter- 

 calary bony segments (vertebrae) of the adult ; thus the embryo 

 suggests an ancestry having a longer neck and tail than exist- 

 ing forms. As some of the Cretaceous Chelonia certainly pos- 

 sessed teeth, ... it is evident that the modern Chelonia 

 are forms that have become separated from their near reptilian 

 relations by specialization. A long-necked ancestry with a 

 fully developed carapace and many bones of the plastron ar- 

 ranged triserially would bring us near the plesiosaurs." 



Parker has figured (plate I, fig. 3) an embryo of Chelone 

 vi7idis Schneid., with fifteen somites in the neck and thirty- 

 six in the remainder of the body. The somites as he has 

 figured them in the neck are very unnaturally crowded and 

 packed, and indeed Parker himself noticed this fact. He says 

 that in the development there are seven "somatomes" lost from 



2. Moodie, 1908, Amer. Jour. Anat., vol. VII, p. 443. 



3. Parker, 1880, Zoology Challenger Expedition, vol. I, pt. V. 



