1922] Notes on the Texas Horned Lizard 131 



brighter in the females than in the males. This we were never able 

 to find true of our Kansas specimens. Also, while Bryant ( '11) states 

 for the entire genus Phrynosoma, that "the presence of enlarged post- 

 anal scales in the male is a dependable character for determining 

 sex," we have not been able to observe such difference in P. cornutum 

 from southern Kansas and northern Oklahoma. In my experience 

 positive separation of the sexes may be made in this species on the 

 following criteria of body form. 



The torso of the males, between axilla and groin, is short and cir- 

 cular; of the females long and elliptical. The tail in the males is 

 longer and distinctly swollen at the root, both laterally and ventrally, 

 due to the contained hemipenes. The tail in the female is shorter and 

 tapers more rapidly from its base backward. It also lacks the basal 

 swellings. The sex of juveniles may likewise be determined on these 

 criteria while that of advanced embrj'cs is apparent from the presence 

 or absence of hemipenes. 



the ovaries 



In females opened early in May and prior to ovulation the ovaries 

 present an interesting picture. Most conspicuous in each is a collection 

 of about sixteen large eggs, yellov/ in color, at first about 7 mm. in 

 diameter but later swelling to 8 or 9 mm. at the time of ovulation, 

 surrounded by delicate follicles and globular in form except for flat- 

 tening due to mutual pressure. 



While the number in each group is not constant there tend to be 

 sixteen, making a total for the two ovaries of about thirty-two large 

 eggs ready for ovulation. In some eases there are but ten or twelve 

 eggs in each large group, in others, and but rarely, seventeen or 

 eighteen. 



Examined separately, each egg displays a germinal disc clearly 

 visible through the follicle and directed toward the point of attach- 

 ment in the mesovarium. The disc is white, circular and about 1^^ 

 mm. in diameter. The borders, although fairly distinct, shade into 

 the surrounding yolk. At the center of the disc is a small, yet dis- 

 tinct, nucleus, about 0.5 mm. in diameter, and clearly discernible in 

 good light to the unaided eye. 



Dorsad of these groups of large eggs ready for la.ying are to be 

 found, in each ovary, eggs of smaller size, two to three mm. in diam- 

 eter, and provided, each, with a small amount of yolk. These smaller 



