Clark — Three Starfish and One Brittle-star from Chile. 155 



Family BENTHOPECTINID.E Verrill. 

 Pectinaster robustus, new species. 



Five arms; R=55 mm. to the distal border of the twentieth supero- 

 marginal, beyond which point none of the arms are preserved ; r=15 mm. 



General form stellate, with narrow pointed rays, very astropectinoid. 



The gonads do not extend into the arms. 



The pedicels have very small sucking disks ; the ampullae are double. 



There are no superambulacral plates. 



The abactinal surface is covered with low paxillae which are very slightly 

 larger just within the arm bases than elsewhere; on the arms they become 

 smaller and more widely spaced, and show a more or less regular arrange- 

 ment in diagonal rows in the lateral portions. There are about twelve 

 paxillse across the arm at the third superomarginal, and about nine at the 

 twentieth. 



The typical paxilke consist of a prominent central spinelet surrounded 

 by from eight to ten shorter and more slender spinelets, usually between 

 one-third and one-half of its length ; some paxillse have two central spine- 

 lets and more numerous lateral spinelets, while others lack the former. 

 In the center of the disk a few of the paxillae have the central spinelet 

 much elongated, up to about 1 mm. in length, and a similar elongation 

 of the central spinelet occurs on scattered paxillae on the arms, becoming 

 more frequent distally. 



The papulae are few, single, confined to a limited, but undifferentiated, 

 area at the base of the rays. 



The two interradial superomarginals are high, narrow, triangular, con- 

 verging actinally ; the second superomarginal is nearly twice as broad, 

 approximately oblong, somewhat over twice as high as long ; the third 

 resembles the second, but is lower, twice as high as long ; the following 

 gradually decrease in height so that the sixth is about as high as long ; 

 the remainder are similar, becoming slightly longer than high at the 

 broken end of the arm (the twentieth) ; the lower border of the supero- 

 marginals is strongly curved so that the seventh and following are almost 

 semicircular in outline, slightly flattened where they adjoin the infero- 

 marginals ; the superomarginals are tumid, with deep grooves between 

 them. The first superomarginal bears a vertical column of four or five 

 spines of which the uppermost is about 1.5 mm. in length, and the fol- 

 lowing progressively shorter ; the second superomarginal bears a column 

 of three spines which are larger and stouter than those on the first ; the 

 third has one large spine, slightly smaller than the spines on the follow- 

 ing superomarginals, and one or two very small spines below it; on the 

 fourth and following there is a single large stout spine situated in the 

 center of the semicircle formed by the lower border ; this reaches a max- 

 imum size on the sixth, where it is about 4 mm. in length. The supero- 

 marginals are bordered, and their surface is covered, with long well spaced 

 spinules which are longest along the lower border; usually two or three 

 of these below and proximal to the large spine are especially elongated. 



The interradial inferomarginals are considerably broader than the cor- 



