REPORT ON THE ECHINOIDEA. 159 



from the trivium. This .species differs from the West Indian Paloeotroinis josephincB, 

 Lov., in being more elongated, in having its greatest breadth near the posterior extremity 

 (PI. XXI. figs. 3, 4). The apical system is anterior (PI. XXI. fig. 3); the apex, on the 

 contrary, is posterior, immediately above the anal system (PI. XXI. fig. 5). Seen from 

 the actinal side the outline is somewhat pentagonal with rounded angles (PI. XXI. fig. 

 4). The actinostome is transverse, very slightly sunken, scarcely labiate (PI. XXI. fig. 

 15), and strengthened by half a dozen large marginal plates (PI. XXI. fig. 8*) with a few 

 irregular smaller plates adjoining the opening ; the actinal plastron is large, covered by 

 large primary tubercles diminishing in size towards the subanal fascicle ; the field enclosed by 

 it is closely crowded by primary tubercles (PI. XXI. fig. 8). The anterior part of the test 

 on the actinal surface is covered by small primaries, extending somewhat above the ambitus 

 (PI. XXI. fig. 5) where the tubereulation of the rest of the abactinal surface becomes uni- 

 form in size (PI. XXI. fig. 3) , the tubercles of the interambulacral areas being larger. 



Seen from the anterior extremity (PI. XXI. fig. 6) there is a row of large primary 

 tubercles in the interambulacral spaces extending from the ambitus to the apical system, 

 which are covered with spines ; the posterior part of the abactinal surface is comparatively 

 bare, carrying minute silk-like spines, gradually increasing in size towards the edge of the 

 ambitus, so that when seen in profile the sides of the test sloping towards the actinal 

 surface are quite thickly covered by long slender spines. The spines also increase in 

 length and size towards the anterior part of the abactinal surface, and are quite prominent 

 in the region adjoining the anterior ambulacral zone (PI. XXI. fig. 11). On the actinal 

 side the spines are closely packed except along the lines of the lateral ambulacral areas, 

 which are left comparatively bare. 



The spines within the subanal plastron form a prominent tuft, cither when seen in pro- 

 file (PI. XXI. fig. 9) or from the actinal side (PL XXI. fig. 10). The test is extremely 

 thin, of a delicate pink colour, with brownish-pink spines. 



Lovdn's individual was a young specimen measuring only about 11 mm., while the 

 smallest specimens collected by the Challenger measured more than 15 mm., and, with the 

 exception of a somewhat less elongate and more globular test posteriorly, agreed well with 

 larger specimens. 



Station 210. January 25, 1875. Lat. 9° 26' N., long. 123° 45' E. ; 375 fathoms ; 

 bottom temperature, 12'2° C. ; mud. 



HoLASTERIDiE. 

 Sub-family HoLASTERiDiE, Pictet. 



It seems at present most natural to place the genera Homolampas, Genicopatagus, 

 Argopatagus, PalcBoi^neustes, and Linopneustes among the Holasteridse rather than with 

 the Spatangidce, but I am not inclined to assign to the Holasteridse the high rank which 



