1894. PROCEEDINGS OF THE NATIONAL MUSEUM. 253 



adambulacral plates are iiariow on the actinal surface, but their inner 

 margin near the adoral end projects into the groove, forming there a 

 prominent angle and leaving deep and broad incurved notches between 

 them; the actinal portion of the projection is rounded and convex, and 

 from its margin arises the furrow- spines, which are nine or ten in num- 

 ber and form an angular group corresponding to the actinal outline of 

 the plate; these spines are subequal, rather slender, elongated, often a 

 little bent outward, and usually laterally compressed and blunt at the 

 tij); they are more or less united at base by a web-like membrane. The 

 small convex actinal surface of the plates bears a central group of about 

 three or four longer, thicker, round or fus:form, usually acute and 

 rou^h spines, similar to the larger ones of the adjacent interradial 

 plates; beside these there are several much smaller, slender spinules 

 on the outer margin in a curved row. The jaw-plates are rather large 

 and thick, Avith sharp, nearly vertical, high inner angles, and with a 

 thick, moderately elevated, actinal keel, separated by a rather wide, 

 elongated median suture. Each jaw-plate bears a row of numerous 

 (about eight) slender spines along the edge, next the groove; these are 

 continuous, with a row of four to six similar spines on the inner, vertical 

 margin. Each actinal keel of the jaw bears two irregular rows of 

 slender, excurved, rough spines, ten or twelve in each row; these spines 

 are similar to the larger ones of the Interradial plates, but are rather 

 more slender. The ambulacra! feet are very large, furnished with 

 a terminal sucker, and occupy the notches between the projecting 

 adambulacral plates. 



Taken by the XJ. S. Fish Commission steamer ^/k^^ross in 1886 at 

 station 2706, off George's Bank, X. lat. 41° 28' 30", W. long. 65° 35' 

 30", in 1,188 fiithoms, 7 specimens (No. 14944, U. S. N. M). Also at 

 other stations in 1883, in 123 and 1,255 fathoms. 



Variations. — The variations, so far as observed, are probably all due 

 to difference of age. The smallest specimen has the lesser radius, 

 12 mm.; the greater, 35mm. This has 27 marginal plates, both above 

 and below. The granulations on the upper marginal plates are more 

 uniform than in the large specimens, those near the lower end of the 

 plate not being much longer than tbe upper ones, but otherwise they 

 have the same character and are pretty evenly spaced. The j)axillne 

 of the dorsal surface are much smaller and mostly circular, or nearly 

 so; the larger ones have three to nine central granules and twelve to 

 eighteen marginal papilhie. The madreporic plate is very small, about 

 midway between the center and the margin. The spinulation of the 

 inferior marginal plates and interradial region is similar to that of the 

 larger examples, excej)t that the spinules are smaller and more slender. 

 In the furrow series each group contains seven or eight spines, which 

 are slender and slightly excurved, but they are arranged as in the adult; 

 the actinal surface of the plate often bears one or two larger central 

 spines, with four or five smaller and more slender ones on the outer 



