464 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.59. 



Among American turtles, the only species in which a sexual differ- 

 ence in color is recorded seems to be Terrayene Carolina (Linnaeus), 

 the common box turtle, in which the eye of the male is red and that 

 of the female brown. 



During the years 1908 to 1912 I collected in Stoughton, Massa- 

 chusetts, and adjacent towns a series of 18 specimens of the spotted 

 turtle, Clemmys guttata (Schneider). All of these were prepared as 

 skins, mounted specimens, or skeletons, and the sex (with the excep- 

 tion of a single young specimen) was determined by dissection in 

 every case. At the close of the first season's collecting I drew up 

 from my series, then amounting to 10 specimens, a table of the 

 sexual differences in coloration, which was confirmed in nearly every 

 respect by later collections of the species. In addition to the mate- 

 rial in my own collection, I have been able, through the kindness of 

 Dr. Leonhard Stejneger, to examine the considerably larger series 

 in the United States National Museum, representing various locali- 

 ties throughout the range of the species. The total number of adult 

 or nearly adult specimens in good condition examined is 60 (24 male, 

 36 female), 17 of which are skins or mounted specimens in my own 

 collection and 43 alcoholics in the National Museum. The sex of 

 the specimens in the latter series has been determined by the ordi- 

 nary external sexual characters of this group — shape of plastron and 

 proportions of tail — and their examination has fully borne out the 

 differences I had found to exist in my own material. The single 

 specimen which departed from these characters was a male, which 

 possessed some of the color characters of the female. It will be 

 described more in detail later in this paper. 



The sexual differences shown in the series examined may be listed 

 in the order of their constancy, as follows: 



1. The horny portion of both jaws in the male is dusky, in the 

 female pale yellow. No exception. 



2. The plastron of the male is distinctly concave along the midline 

 near the anterior margin of the femoral shields; that of the female is 

 flat or slightly convex essentially throughout. Occasional females 

 have a slight transverse depression extending across the plastron at 

 about the anterior margin of the femorals, but this never assumes 

 the character of a central depression such as is found in the males. 



3. The female has a conspicuous yellow or orange mandibular 

 stripe reaching about half the length of the neck; the male has a few 

 spots or almost none, or rarely a weak streak about 5 mm. long. The 

 only exception is the aberrant male mentioned above, which has a 

 rather strong mandibular stripe. 



4. The throat of the male is black, with sparse and usually 

 obscure, rarely numerous, small yellow specks; that of the female 

 is heavily streaked and spotted with yellow, usually aggregated for- 



