PREFACE. XI 



to the inner branch of the second pleopod, in this respect being- coni- 

 para])le to Dynamene {Nvem) Leach and AiH-!nella Hansen. I there- 

 fore make this species the t^^pe of a new oenns Di/naiiienwcus. 



Doctor Hansen says that Sphxrorna yiir<it(()tiiiii has been established 

 on females or young- males of animals belonging- to the genus Cymo- 

 (Idce. The only specimen is a young femal(\ 



Toward the end of his paper Doctor Hansen makes the statement 

 that the species Tecticeps eonvej-us was estal)lished on the female form 

 of Tectictpx aJascensM, and therefore cancels the tirst-named species. 

 As Doctor Hansen had seen only the two sexes of Tecticeps alasceihns 

 and had not seen any specimens of Tecticeps coiwexiiM^ this error was a 

 natural one. Inasmuch as both sexes of both species are in the col- 

 lection of the U. S. National Museum, it would be well to point out 

 the sexual differences as perhaps I have not done sufficiently hereto- 

 fore or even in the pages to follow. The females of l)t)th TcctlcepH 

 alascensis and Tecticejys convexus differ from the males in having- the 

 second pair of legs ambulatory and similar in stracture to those fol- 

 lowing, while in the males the second pair of legs are subchelate. The 

 female of Tecticeps alascensis has the exopod of the uropod not longer 

 than the endopod, and thus differs from the male. Which has the exo- 

 yjod longer than the endopod. In the species T. eonve.rtfs, however, 

 the exopod of the uropod is equal in length to the endopod in both 

 sexes. The females of the two species are quite similar, ])oth having 

 the exopod of the uropod short, but the}' can easil}" be distinguished 

 b}' the difference in the position of the e3'es, the difference in the shape 

 of the extremity of the terminal al)dominal segment, and the difference 

 in the length of the antenna\ Male specimens are compared in the 

 pages to follow, and the differences given in the key are from a com- 

 parison of males. It is to l)e hoped that with these additional notes 

 no difficulty will be found in distinguishing the two species, and that 

 the validity of Tecticeps convexus, heretofore established, is correctly 

 maintained. 



H. K. 



Washington City, December 1, 1905. 



