648 



THE VOYAGE OF H.M.S. CHALLENGER. 



Chore-logical Synopsis of the Species. 



1. Colpaster seutigerula, n. sp. (PI. CXVII. figs. 4-7). 



Pays seven. E = ? mm. ; r = 6 mm. Breadth of a ray at the base, 5 mm. ; at the 

 widest part of the ovarial inflation, 5 - 5 mm. (measured at 9 mm. from the disk); and at 

 24 mm. from the disk, 4 mm. 



The rays are robust at the base in proportion to the small disk, and have a very 

 slightly fusiform ovarial inflation, which does not extend beyond 18 mm. from the disk. 

 Beyond the ovarial inflation the ray is subtriangular, with a broad median carination. 



The disk is small and rather thick, with the lateral walls precipitous, and the margin 

 slightly incurved in the interradia, and slightly tumid over the base of the rays. The 

 abactinal surface is covered with small imbricating plates, which bear from three to six 

 small equal-sized spinelets less than 0"5 mm. in length ; their shafts are cylindrical, flaring 

 slightly at the tip, with four or five thornlets. One or two small pedicellarise may be 

 seen here and there at the base of the spinelets, but there are very few. The abactinal 

 surface of the rays is covered (at least at the base) with similar small imbricating plates, 

 which diminish very considerably in size as soon as the ovarial region is passed. They 

 are present throughout the whole length of the fragments under notice, and I am there- 

 fore unable to say how far they extend along the ray. The plates on the ovarial regions 

 bear similar, but rather smaller, spinelets than those on the disk, and they decrease in 

 number on the outer part of the region. Numerous small pedicellarise are upon the 

 plates and increase in number as the spines decrease, but no trace of sacculi with crowded 

 pedicellarite are discernible on the innermost 28 mm. of the ray. 



The ambulaeral furrow is wide, measuring 2*25 mm. in breadth at a part where the 

 ray is 4 mm. The adambulacral plates are very little if at all longer than broad at the 

 outermost end of the fragments, where they measure about 1*3 mm. in length ; they are 

 separated by a wide space filled in with ligament, and the furrow-margin of the plate is 

 slightly concave. The adambulacral armature consists of : — (1.) two small inner spines, one 

 at each extremity of the plate, directed over the furrow; (2.) two unequal actinal spines, 

 which stand perpendicularly or slightly inclined towards the furrow; (3.) a lateral spine, 

 perhaps normally borne on alternate plates, but frequently on consecutive plates on the 

 basal part of the ray. The small inner spines, which are subequal, are a trifle more 

 than 1 mm. in length, cylindrical, delicate, and only slightly tapering ; they are covered 



