62 THE VOYAGE OF H.M.S. CHALLENGEK. 



equal length, the last conical in form and terminating in a strong spine ; of lateral 

 denticles there are only three (one on the first and two on the last joint). The outer 

 branch exhibits the usual form, its terminal joint being rather slender and provided 

 with a few small hairdike bristles on both edges, and a somewhat stronger apical seta. 



Habitat. — The above described specimen was taken together with the preceding 

 form at Station 79, July 11, 1873; lat. 36° 21' N., long. 23° 31' W.; depth, 2025 

 fathoms ; bottom, Globigerina ooze ; bottom temperature, 35°'9. 



Family VI. Cumellid^e. 



The Cumacea comprised within this family are generally very small, and at once 

 distinguished by the very slender form of the three posterior pairs of legs, which more- 

 over terminate in a strong curved claw. They also differ considerably from the 

 Cumacea belonging to the preceding families, by the male wanting every trace of 

 pleopoda. The family comprises two distinct genera, easily recognisable by the very 

 different structure of the visual organ, viz., Cumella, G. 0. Sars, and Nannastacus, 

 Spence Bate. Moreover, I am inclined to regard the genus Spencebatea, established by 

 Norman, on a single male specimen procured by the " Porcupine " expedition, as belonging 

 to this family. Of these three genera only the genus Nannastacus is represented in 

 the Challenger collection. 



Genus Nannastacus, Spence Bate, 1865. 



Nannastacus, Spence Bate, Carcinological Gleanings, No. 1, Ann. and Mag. Nat. Hist., 1865. 

 Diops, Paulisona, Tzsljedovanija rakoobraznjikh krasnago raorja, p. 128, 1875. 



Generic Characters. — Carapace large, not cristated above, with the antero-lateral 

 corners more or less produced. Eyes distinctly separated, with well-marked visual 

 elements. Antennulaa with one of the flagella rudimentary. Antennas in female very 

 minute, uniarticulate, and provided with three strong hairy setae, in male shorter than 

 body. First pair of legs with terminal part slender and strongly geniculate; second 

 pair much shorter. The three posterior pairs of legs very slender and nearly equal in 

 length; terminal claw very strong. Uropoda with the branches very unequal, inner 

 much larger than outer, and composed of a single joint, strongly spinous at the inner 

 edge. 



Remarks. — This genus, established by Spence Bate for the reception of a peculiar 

 little Cumacean — described by the same author at an earlier date as Cuma unguiculata — 

 is chiefly distinguished by the eyes being widely separated, and never, as in the other 

 Cumacea, confluent. In other respects it comes very near to the genus Cumella. 



