52 Journal of the Mitchell Society [September 



bodies of the turtle. The results of his later investigation were pub- 

 lished (1848) under the title "Entwicklung der Schildkroeten. " In 

 this work he deals chiefly with gross anatomy of various stages of 

 development, especially of the muscles, the carapace, and the ali- 

 mentary canal. 



Nothing more of importance appeared on this subject until 1857 

 when the classic work of Agassiz was published, which, according to 

 Davenport (1898), "stands today with its many unverified facts as 

 an incentive to the reptilian embryologist. " Since Agassiz 's time no 

 one has attempted to work completely over the field of turtle embry- 

 ology, although numerous short articles have been written. 



The Collection of Material 



The materials used in the preparation of this paper were col- 

 lected in the vicinity of Madison, Wisconsin. The territory around 

 Lake Wingra furnished most of the specimens taken on land. Col- 

 lections were made also on Lake Mendota, Lake Monona and on Mud 

 Lake. A number of turtles were taken from high land, since the 

 object was to capture them when nest building, but the majority 

 were caught with dip nets in the water. 



There seems to be considerable confusion as to the synonymy of 

 four of the so-called "species" of Chrysemys, viz. Chrysemys margi- 

 nata Agassiz; C. hellii Gray; C cinerea Bonnaterre; and C. picta 

 Hermann. Chrysemys cinerea was named by Bonnaterre probably 

 between 1790 and 1800. Chrysemys hellii was named by Gray early 

 in the nineteenth century, while C. picta was designated as Testudo 

 picta by Hermann before 1792. 



Agassiz recognized the validity of all four species. His differ- 

 entiation, however, was built largely upon the color pattern which 

 may easily be shown to be a false basis. In his description he indi- 

 cates that the arrangement of the vertebral plates in C. picta differ- 

 entiates it from all other forms. While some of his figures bear out 

 this idea, the others do not. An examination of figures 1 to 6 will 

 make this clear. Figure 2 is C. maryinnta while all the other are C. 

 picta. The similarity of figures 2 and 5 is so striking in regard to 

 vertebral plate arrangement that no one would think of making 

 them into two species. Figures 1, 3, and 5 seem to form a graded 

 series from the typical C. picta to the typical C. maryinain. 



Gadow's (1901) figure of C. picta (figure 7), is intermediate be- 



