4 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 9I 



those succeeding are closer together. They are somewhat obhque, 

 their tips being farther from the arm base than their bases. 



Between the inferomarginals and the adambulacral plates and 

 adjoining each is a single continuous row of actinal plates. There 

 are two of these under the first inferomarginal, and one long narrow 

 one under each of those following. 



There are 13 or 14 adambulacral plates. These at first are slightly 

 broader than long, becoming about as long as broad distally. 



The tube feet, which have large sucking disks, are in two rows. 



All the plates of the abactinal surface bear numerous — up to a 

 dozen or more — short stout spinelets. These have a broad base, a 

 narrowed column, and the outer half swollen and club-shaped, echinu- 

 late, with a broadly rounded tip. These spinelets are set upon the 

 swollen portions of the plates more or less in contact by their broad 

 bases. On the longer plates there are commonly five or six along 

 each side, with one or two additional between the rows. On the 

 more rounded plates there may be six peripheral and one central. 

 They form a very even investment of the abactinal and lateral 

 surfaces. 



Each superomarginal bears 10 or 11 of these spinelets, exactly 

 resembling those on the abactinal surface. There are 8 to 10 around 

 the swollen central portion, and i or 2 in the middle. 



The upper surface of the produced inferomarginals bears eight 

 or nine of these spinelets, commonly arranged in two rows of four 

 or five each, though sometimes irregular. The outermost of these 

 are swollen for their whole length, and therefore appear larger than 

 the others. At the tip of the pillarlike production are three longer, 

 much stouter, strongly echinulate rounded conical somewhat flattened 

 spines. On the actinal side the inferomarginal bears from four to 

 six small slender echinulate spinules without swollen ends which are 

 well separated from each other. 



The two basal actinal plates bear three spinules resembling these, 

 but more than twice as large ; the actinal plates following bear first 

 two, then one, and distally none. 



The first three adambulacral plates bear a comb of four rather long 

 echinulate furrow spines that are webbed for about half their length ; 

 the combs on the following adambulacrals consist of three spines. 

 These combs are set obliquely, making an angle of about 45° with 

 the furrow. On the outer portion of the adambulacral plates, away 

 from the furrow margin, is another oblique comb of three similar 

 spines, less completely webbed. 



