332 VERRILL 



fasciolated spinules becoming very short. These distal plates have a 

 slightly granular surface, but no articulated granules. Most of the 

 inferomarginals bear a small, subacute, articulated spine or tubercle 

 near the upper end. 



The actinal plates, in specimens of ordinary adult size, form six 

 double rows,' running from the six interradial inferomarginal plates 

 to twelve adambulacral plates. The plates are small next the mar- 

 ginals, but become much larger toward the adambulacrals ; they are 

 smooth, flat, irregularly angular, with rounded corners, and alternate 

 closely in the two rows, without intervening grooves or spinules ; 

 their united edges overlap slightly. 



Sometimes there are slight irregularities in this arrangement ; the 

 more distal of the double rows may correspond with but one adambu- 

 lacral, on some of the rays. Farther out the marginal and adambu- 

 lacral plates correspond, and there are but two (or only one) actinal 

 plates between them. Beyond the sixth marginal, the remaining 

 five or six are joined directly to the adambulacrals. 



The fasciolated grooves run directly from between all the infero- 

 marginal plates to the ambulacral grooves, thus passing between the 

 double rows of actinals ; and distally between all the marginals and 

 adambulacral plates. They are bordered by regular, close, single 

 rows of short appressed spinules. 



The adambulacral plates are large and have a strong triangular 

 lobe projecting into the grooves, ending in line with a sharp ridge 

 that stands between the large ambulacral feet. The proximal plates 

 bear a series of three or four (sometimes five) acute, divergent 

 furrow-spines ; the distal ones, only two spines ; on the actinal side 

 there may be three to five small spines, mostly marginal. Oral spines 

 numerous, the two medial adorals stouter. 



Color, light yellow to pale orange, the upper surface often gray 

 when the stomach is distended with mud, as it frequently is. 



The median dorsal nephridial cone is usually low in the adults, 

 but elongated in the very young ones. The central pore is minute. 



I have studied a considerable number of regular four-rayed 

 specimens taken off the coast of New England by myself and by the 

 U. S. Fish Commission. 



This species is abundant in the North Atlantic and Arctic Oceans, 

 on soft muddy bottoms, in from lo to 650 fathoms. It is found on 



' The detailed figure of these plates, given by Muller and Troschel, is in- 

 correct, as to their regular arrangement in double and single columns. (See 

 pi. XLix, fig. 5. copied from Muller and Troschel, and pi. v, fig. 6.) 



