1296 THE VOYAGE OF H.M.S. CHALLENGER. 



they been found associated, they might have been supposed to be sexually related." 1 

 There are objections to that particular inference from the fact, but the fact itself of their 

 being found associated is highly probable, since Mr. Spence Bate records a Cyllopus and 

 a Vibilia from the same habitat " near the Powel Islands," and the Challenger specimen 

 of Cyllopus bears the same date of capture as specimens of Vibilia. 



Genus Cyllopus, Dana, 1852. 



1852. Cyllopus, Dana, U.S. Explor. Exped., vol. xiii. pt. ii. pp. 981, 989, 1519.- 



1862. „ Spence Bate, Brit. Mus. Catal. Amph. Crust., p. 305. 



1887. ,, Bovallius, Systematical List of Amph. Hyper., Bihang till K. Svensk. Vetensk. 



Akad. Hand!, Bd. 11, No. 16, p. 11. 

 1887. „ Bovallius, Arctic and Antarctic Hyperids, Vega-Exped., Bd. iv. p. 555. 



For the original definition of the genus, see Note on Dana, 1852 (p. 268). Bovallius 

 in 1887 defines it as follows : — 



"Head globular, a little tumid. Eyes large, filling almost the whole sides' of the 

 head. First pair of pereiopoda [first gnathopods] simple or subchelate. Second pair 

 with a more or less produced carpal process. Femur of seventh pair [first joint of fifth 

 perseopodsj much longer than the following joints together. Telson small, rounded." 



The epithet " rounded " is scarcely applicable to the telson, since in Cyllopus lucasii, 

 Spence Bate, it is said to be lanceolate. Spence Bate notices in regard to the species 

 which he calls " Cyllopus magellanicus," that the second joint of the mandibular palp is 

 the longest. This is the case in the Challenger specimen, and if it be a character of all the 

 species it would be convenient to include it in the generic definition. Cyllopus magel- 

 lanicus, Spence Bate, is distinguished by Bovallius from Dana's species of that name, and 

 renamed " Cyllopus Batei." 



Cyllopus hookeri, n. sp. 



Head with a small rostral angle between the upper antennae ; back rounded ; first 

 three segments of the pleon with convex lower margins, serrate near the rounded postero- 

 lateral angles ; the coalesced fifth and sixth segments have the line of coalescence 

 marked by a slightly convex groove at the centre of the back equal to about a quarter of 

 the dorsal breadth. 



Eyes dark, occupying almost the entire surface of the head ; many of the multitudinous 

 ocelli are very small, the crystal cone being in some cases spherical. 



Upper Antennae. — The first joint of the peduncle longer than the two following 



1 Brit. Mus. Catal., p. 305. 



2 It was no doubt by an oversight that Dana omitted Cyllopus from the classification of the Hyperidea at page 144l'. 



