70 Journal of the ^Iitchell Society [September 



figured by Agassiz (1. c). In fact, Agassiz (see Agassiz, plate 9-e) 

 makes the head fold the first to develop. Certainly, such is not the 

 case in Chrysemys cinerea. 



Summary 



1. Chrysemys cinerea is shown to be the only species occurring in 

 the vicinity of Madison, Wisconsin. 



(a) There are no constant differences of markings in the forms 

 occurring there by which C. cinerea and C. bcllii can be separated. 



(b) Chrysemys marginata and Chrysemys cinerea have been 

 previously combined as a single species, the latter name being adopted 

 on the basis of priority. The impossibility of differentiation between 

 C. cinerea and C. heUii requires that but one species be recognized. 

 Priority designates it as C. cinerea. 



(c) While hybridization is possible, the undiminished fecundity 

 of these forms indicates that they are not hybrids. 



(d) It is more probable that geographical varieties occur in dif- 

 ferent regions, as is the case with the song sparrow, 



2. The egg-laying period was found to extend from June 8 to 

 June 26, with a possible extension of time to July 7. Turtles were 

 observed in oviposition from 3 :30 p. m. to 6 :00 p. m., but indications 

 were that egg-laying may be carried on any time from 12 :00 m. to 

 10 :00 p. m. 



3. It was found that the supernumerary bladder is used for moist- 

 ening the soil in digging the nest. That the water contained therein 

 was excretory in nature. 



4. The number of eggs in a clutch varies from four to fourteen. 

 The number of eggs in the ''groups" in the ovary varies from one 

 upwards to fifteen. 



5. Chrysemys cinerea may begin laying when it reaches a length 

 of one hundred and thirtj' millimeters and, apparently, there is a 

 relation between the size of the turtle and the number of eggs laid. 



6. The nests are opened by some unknown animal which destroys 

 the eggs. This led to the use of artificial incubation. 



7. The possibility of artificial incubation has been shown and suc- 

 cessful methods have been described. 



8. Uterine eggs may be used with even better results than can be 

 obtained with laid eggs. 



