60 Proceedings of the Biological Society of Washington. 



Family ECHINASTERID^ Verrill. 

 Echinaster parvispinus new species. 



Five arras; R=53mm.; r=10mm.; R:r=5.3:l. 



The arms are robust, evenly tapering. 



Tlie abactinal plates are tliick and heavy, but relatively small, arranged 

 in three regular rows along the dorsal (abactinal) surface of the arms, 

 with three additional irregular rows between the outermost of the dorsal 

 rows and the superomarginals. The three dorsal rows of plates, which 

 are about 2 mm. apart, form three rather prominent narrow and irregular 

 ridges, and bear numerous short conical or cylindrical, sometimes capitate, 

 jointed spines, usually two or three to a plate, which rarely reach 1 mm. 

 in height, in an irregular zigzag series ; in the carinal row there are 

 about forty-five of these spines from the base to the tip of the arm. 



The plates of the lateral rows are somewhat less regular in disposition, 

 and are less elevated. The spines which they bear are more slender than 

 the spines of the three median series, though not much smaller; this, 

 combined with the lesser elevation of the plates, serves to make the lateral 

 plates and spines noticeably less conspicuous than the median. The 

 plates in these lateral rows are more numerous than those in the median, 

 there being four in the former to three in the latter. In the lateral rows 

 there is only one spine to a plate. 



The center of the abactinal area bears scattered spines which are similar 

 to those of the three median rows on the arms. 



The madreporite is oval, about 2 mm. in the greater diameter, bearing 

 short peripheral spines. 



Papulfe are very abundant, in alcoholic specimens often appearing to 

 form broad continuous lines which extend the whole length of the arms 

 between the rows of spines. Single intermarginal papulfe may occur, 

 especially toward the ends of the arms. 



The superomarginals, which form a continuous band all along the arm, 

 are irregular in shape, longer than broad; their spines, one to a plate, 

 form a regular line all along the arm, and are similar in character to the 

 spines on the plates above. 



The inferomarginals proximally bear two (rarely three) spines similar 

 to those of the superomarginals in a transverse series, these becoming 

 reduced to one in the outer half of the arms. 



In the actinal interradial areas only the spines of the inferomarginal 

 series occur; these are commonly much reduced in size, and sometimes 

 obsolete. 



On the adambulacral plates the furrow series consists of three spines; 

 the first of these is very small, recurved, situated on the inner face of the 

 plate near the bottom of the groove ; the next is nearly or quite twice as 

 long, slender, situated half way up on the inner face, and the third is 

 much stouter than the two preceding, situated on the inner border of 

 the plate. Behind this third spine is another much smaller spine on 

 the actinal surface of the plate. 



Color in alcohol usually dark purplish or reddish brown, sometimes 

 light pink. 



