104 THE VOYAGE OF H.M.S. CHALLENGER. 
Chorological Synopsis of the Species. 
| Ocean. | Range in Fathoms. | Nature of the Sea-bottom. 
| ; 
Lonchotaster forcipifer . . | Southern Ocean. 1950 to 1975 | Diatom ooze. 
| Lonchotaster tartareus : : | Atlantic. 2400 Globigerina ooze. 
1. Lonchotaster tartareus, u. sp. (Pl. XVI. figs. 1-5). 
Rays five. In the largest specimen R = 88 + mm., 7 = 20°5 mm. Breadth of the 
ray at the sixth supero-marginal plate, 16 mm. (The tip is wanting in all the rays of this 
example.) In a smaller but perfect example R= 55 mm.,r = 14 mm. Breadth of the 
ray at the sixth supero-marginal plate, 9°5 mm, 
Rays moderately elongate and comparatively narrow, tapering gradually to a pointed 
extremity, the outer part of the ray being attenuate and subcylindrical. Interbrachial 
ares wide, open, and well rounded. Abactinal area convex and more or less inflated. 
Actinal area plane. Lateral walls low, very slightly rounded. In all the specimens 
collected the rays are sharply turned back over the disk, nearly from their base. 
The abactinal area of the disk and rays is covered with numerous small and closely 
packed paxillz ; these are composed of ten to fifteen small, erect, cylindrical, obtusely 
rounded, skin-covered papille, three to five being central. In a very large number of the 
paxillze two to four of the central papille are enlarged and form a pedicellarian apparatus. 
In consequence of their skin investiture and erect position the separate papille are not 
noticeable to the naked eye, only the paxille as a whole being distinguished ; the paxillar 
area In consequence has a smooth and highly compact appearance. The paxille present 
no definite order of arrangement. 
The marginal plates are small and confined entirely to the lateral wall of the ray. The 
supero-marginal plates are forty-five in number counting from the median interradial line 
of the longest remaining ray, from which, however, the tip has been broken in the large 
specimen, with an estimated loss of twenty to thirty plates. Fifty-three are present from the 
median interradial line to the extremity in a smaller example in which R= 55mm. The 
plates are rectangular, with the height rather greater than the length on the inner part of 
the ray, but subequal on the outer part ; and only the upper edge of the plate is visible 
on the abactinal surface. The plates are covered with low granule-like papille, often 
somewhat squamiform, but longer, more delicate, and cilia-like along the lateral sutures. 
The supero-marginal plates are devoid of any true spines, but within the interbrachial are 
and at the base of the rays in the large example, a small conical tubercle is present close to 
the upper end of the plate, but it is not found in the smaller specimens. On some of the 
plates three or four of the papillz are slightly enlarged and form an incipient pedicellarian 
