PREFACE. XI 



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

 parable to Di/iinim ne (Nsesa) Leach and Ancinella Hansen. I there- 

 fore make this species the type of a new genus Dynameniscus. 



Doctor Hansen says that Sphserama yucatanum has been established 

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

 doce. The only specimen is a young female. 



Toward the end of his paper Doctor Hansen makes the statement 

 that the species Tecticeps convexm was established on the female form 

 of Tectiecpx alascensis, and therefore cancels the first-named species. 

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

 and had not seen any specimens of Tecticeps convevus, 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 both Tecticeps 

 olti.ycensis and Tecticeps convexus differ from the males in having the 

 second pair of legs ambulatory and similar in structure 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- 

 pod longer than the endopod. In the species T. convexus, 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, both having 

 the exopod of the uropod short, but they can easily be distinguished 

 by the difference in the position of the eyes, the difference in the shape 

 of the extremity of the terminal abdominal segment, and the difference 

 in the length of the antennge. 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 be 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. R. 



WASHINGTON CITY, December 1, 1905. 



