534 



BULLETIN 54, UNITED STATES NATIONAL MUSEUM. 



lateral portions of lifth seo-nient end in a sharp crest, and there is no 

 'shield.' The sixth segment is very long-; it narrows posteriori}', 

 has a tlesh}' median keel and only slighth^ developed lateral por- 

 tions. The seventh segment is short, fleshy, about as wide as sixth 



Fig. 579.— Stegophkyxus hyptius (Akter Thompson), n, Dors.\l view ok ahvlt mai.e. x 12. 

 6, Ventral side of head of same, x 22. c, Ventral view of head of cryptoniscid. x 110. 

 d, Cryptoniscid from young female (lateral view), x 58. e, Pleopod of third abdominal 

 segment of cryptoniscid. X 70. /, Musculature of one of first four pereiopoda (adult 

 female). X 20. g. Musculature of one of sixth or seventh pereiopoda of female, x 20. 

 h, Musculature of pereiopod. x 40. /, Dorsal viem' of larval female, x 12. j, Ventral 

 view of same, x 6j. 



and similar to it, except that it is not keeled. Ventral surface of 

 thoracic segment fleshy, posterior borders of sixth and seventh modi- 

 fied into complex elevated keels. Pereiopoda of the sixth and seventh 

 segments are alike and quite simple in construction; those of the other 



