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. 
8. Bathymetrical range: 1240 to 1700 fathoms. The form is thus confined to the 
Abyssal zone. 
y. Nature of the Sea-bottom: Blue mud. 
Chorological Synopsis of the Species. 
Ocean. Range in Fathoms. | Nature of the Sea-bottom. 
ls 
| 
| Phowxaster pumilus . : . | Atlantic. 1240 to 1700 | Blue mud. 
1. Phoxaster pumilus, n. sp. (Pl. XL. figs. 3-6; Pl. XV. figs. 7-11). 
Rays five. R=31 mm.; r=75 mm. R>4r. Breadth of a ray at the third 
supero-marginal plate, 7 mm. 
Rays 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 paxille. These are composed of four to seven short, equal, truncate, granuliform, 
skin-covered papillze, which fit close together subprismatically, with one often central in 
the larger paxille, but by no means invariably. The paxille 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 rays, the successive series being 
more widely spaced than the paxillze 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- 
