234 c - L - TURNER. 



instance the additional hooks were carried upon the fourth 

 walking legs and in the other upon the second walking legs. 



In July, 1923, a collection was made from a tributary of 

 Turtle Creek twelve miles from the first locality. Of 150 males 

 five had additional copulatory hooks. Three of these had 

 well developed additional hooks upon the second walking legs 

 while the other two specimens bore the extra hooks upon the 

 fourth walking legs. 



A single specimen from a collection of twenty-five males from 

 Delavan Lake had extra copulatory hooks upon the fourth 

 walking legs. 



A collection of 152 male specimens from a tributary of Rock 

 River twelve miles south of Turtle Creek contained three with 

 extra male hooks, two of them bearing the extra hooks upon the 

 second walking legs and the other bearing them upon the fourth 

 walking legs. 



3. Cambarus obscurus. 



A small collection of thirty-eight males from Ashtabula, Ohio 

 w r as examined at Ohio State University and one male was found 

 with extra copulatory hooks upon the second walking legs. 



4. Other Species of Cambarus. 



An examination of 1280 specimens from eight additional species 

 of Cambarus failed to bring to light any new aberrant specimens. 



DISCUSSION AND SUMMARY. 



The records cited above are quite limited but a few general facts 

 become apparent when they are examined critically. 



I. Supernumerary male secondary sexual characters seem to 

 differ with the species in which they occur. An examination of 

 600 specimens of Cambarus clarkii failed to reveal any deviations 

 from the usual male secondary sexual characters either in the 

 copulatory hooks upon the third and fourth walking legs or in the 

 modified appendages of the first and second abdominal segments. 

 An examination of 310 specimens from three species of the 

 subgenus Faxonius likewise failed to show any aberrant features. 

 On the other hand there is a rather constant occurrence of 

 additional copulatory hooks in Cambarus propinquus as repre- 

 sented by specimens from southern Wisconsin, northern Illinois 



