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



Chorology of the Genus Phoxaster. 

 a. Geographical distribution : — 



Atlantic : One species between the parallels of 35° and 45° N. 



Phoxaster pumilus off the eastern coast of the United States of 

 North America. 



/3. Bathymetrical range: 1240 to 1700 fathoms. The form is thus confined to the 

 Abyssal zone. 



y. Nature of the Sea-bottom : Blue mud. 



Clwrological Synopsis of the Species. 



1. Phoxaster pumilus, n. sp. (PL XL. figs. 3-6 ; PL XV. figs. 7-11). 



Pays five. R = 31 mm.; r=7"5 mm. R > 4 r. Breadth of a ray at the third 

 supero-marginal plate, 7 mm. 



Pays moderately elongate and robust, tapering from the base to the extremity, which 

 is rather abruptly pointed. Lateral walls high and nearly vertical. Abactinal area 

 subplane, with a prominent and well-defined, though small, epiproctal . protuberance. 

 Actinal area merging into the rounding of the lateral wall. Interbrachial arcs acutely 

 rounded. 



The abactinal paxillar area of the disk and rays is covered with numerous small, com- 

 pact paxillse. These are composed of four to seven short, equal, truncate, granuliform, 

 skin-covered papilla, which fit close together subprisrnatically, with one often central in 

 the larger paxillae, but by no means invariably. The paxillas diminish in size as they 

 approach the centre of the disk, and become almost indistinguishable on the central peak- 

 like protuberance. A more or less regular arrangement in transverse series may be 

 distinguished at the margin along the inner half of the ravs, the successive series being 

 more widely spaced than the paxillse in each series. 



The supero-marginal plates, forty in number from the median interradial line to the 

 extremity, are very short and high, standing vertically, and confined entirely to the lateral 

 wall of the ray, forming, however, an abrupt, sloping, and rounded bevel to the abactinal area. 

 In relation to one another the surface of the plates forms a continuous plane. On the inner- 



