A PPEND TX— GR USTA GEA . 127 



Allorchesfes, and discriminates the species themselves by characters relatiiijj; 

 t(» the branchiee not noticed in earlier descriptions. 



Hyalella inermis received its name to distinguish it froni the allied species 

 Hijalella dentata, which has the first and second segments of the abdomen or 

 pleon "with the dorsal margin produced posteriorly into a well-marked spini- 

 forni tooth." In these species the second gnathopod or clasper is very differ- 

 ent in the two sexes, the hand in the male being greatly developed and set 

 in the short transverse wrist ; while in the female hand and wrist are in a 

 continuous line, about equal in length, (juite small and thin. 



