256 VERRILL 



The madreporic plate is large and has four pseudopaxillae on its 

 surface, and others irregularly placed at its margin. 



The adambulacral spines in the furrow-series are short, and stand 

 mostly three to a plate, the middle one longest; but at about the 

 distal fourth of the rays they are reduced to two. The actinal trans- 

 verse combs consist proximally of about eight to ten webbed and 

 feebly graded spines, in a simple, slightly curved row, the inner 

 ones slightly longer and larger than the middle ones ; but, owing to 

 the convex summit of the plate, the middle spines are often more 

 prominent and the tips form a curved outline; the outer ones are 

 much shorter. 



The inferomarginal plates are transversely oblong and often com- 

 pressed. Each bears a marginal, webbed series of about eight to ten 

 rather strong spinules on each side, and often a partial median row 

 of two to four spinules. 



The superomarginal plates are small, rounded or ovate, close to the 

 inferomarginals, and bear a stellate group usually of five to seven 

 spinules, like those of the dorsal surface. 



The actinal interradial areas are relatively small and narrow, and 

 are covered by small, rounded, unequal pseudopaxillae, which form 

 about eight radial rows distally. They mostly bear four to six, 

 rarely eight, stout spinules in a stellate, webbed group, rarely with a 

 central one. Their spinules are like those of the adjacent infero- 

 marginal plates, but fewer. 



The peroral spines consist of a terminal group of six stout, close, 

 graded, subacute spines, with three or four much smaller spines on 

 each side. The epiorals consist of two opposed curved and con- 

 vergent rows of seven to nine graded spines, often with the opposed 

 tips in contact or interlocking, the two inner ones decidedly stouter. 



Pedicellariae of minute size occur in this species. They were first 

 observed by A. H. Verrill, while drawing the details of the dorsal 

 pseudopaxillae mounted for the microscope. They are very small, 

 sessile around the papular pores, bivalve, often with the valves 

 unequal. (See pi. xlvi, fig. ic.) They are scarcely visible to the 

 naked eye and occur only in small numbers, so far as observed, and 

 are, therefore, likely to be overlooked. Some specimens seem to lack 

 them entirely. 



This species has a wide range, from Oregon to the Aleutian 

 Islands, and, according to Fisher, has been taken also farther north, 

 at Bering Island, Commander Islands group. 



Dr. Fisher records it from low tide to 33 fathoms, and from 

 Oregon to Bering Island. 



