104 



THE VOYAGE OF E.M.S. CHALLENGER. 



1. Lonchotaster tartareus, n. sp. (PI. XVI. figs. 1-5). 



Bays five. In the largest specimen B = 88 + mm., r = 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. 



Bays moderately elongate and eonrparatively narrow, tapering gradually to a pointed 

 extremity, the outer part of the ray being attenuate and subcylindrical. Interbrachial 

 arcs 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 paxilhe ; these are composed of ten to fifteen small, erect, cylindrical, obtusely 

 rounded, skin-covered papdlae, three to five being central. In a very large number of the 

 paxillEe two to four of the central papillae are enlarged and form a pedicellarian apparatus. 

 Iu consequence of their skin investiture and erect position the separate papillae are not 

 noticeable to the naked eye, only the paxillse as a whole being distinguished ; the paxillar 

 area in consequence has a smooth and highly compact appearance. The paxillse 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 iu a smaller example in which R = 55 mm. 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 papilla), 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 arc 

 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 papilla; are slightly enlarged and form an incipient pedicellarian 



