648 THE VOYAGE OF H.M.S. CHALLENGER. 
Chorological Synopsis of the Species. 
| Ocean. Range in Fathoms. | Nature of the Sea-bottom. 
Colpaster scutigerula . ‘ Atlantic. 1525 | Hard ground. 
1. Colpaster scutigerula, n. sp. (Pl. CXVII. figs. 4-7). 
Rays seven. R=%mm.; 7 =6mm. 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 pedicellarize 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 pedicellarize are upon the 
plates and increase in number as the spines decrease, but no trace of sacculi with crowded 
pedicellarize are discernible on the innermost 28 mm. of the ray. 
The ambulacral furrow is wide, measuring 2°25 mm. in breadth at a part where the 
ray is 4mm. 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 
