212 ECHINODERMA OF THE INDIAN MuSEUM, PART VII. 



involve more and more of the dorsal surface of the segments, which become 

 carinate, so that after the twenty-third the dorsal profile (in lateral view) is 

 straight and parallel to the longitudinal axis of the cirrus as a whole ; in the 

 next four to seven segments a shallow rounded notch is developed in this straight 

 dorsal jDrofile, so that the segments tippear to have both a proximal and a distal 

 spine ; beyond this point the dorsal processes are of the high strongly carinate 

 type common to the other species of the genus. 



Ends of the basal rays visible in the angles of the calyx, just over the ridges 

 separating the individual columns of cutus sockets in the interradial pairs, as 

 small dorsoventrally elongate tubercles ; radials almost entiiely concealed; they 

 bear on their apposed edges, just over the ends of the basal rays, two tubercles 

 or blunt spines, one on each radial. IBr, extremely short, six or more times 

 as broad as long, chevron-shaped, with both the anterior and the posterior edges 

 prominently everted, smooth, somewhat wavy, or coarsely tubercular; in the 

 middorsal hne there is a prominent median rouiulcd carination. The arms are 

 lost beyond this point. 



Locality. — "Investigator''' Station 232; i'M fathoms. — Two specimens. 

 Remarks. — This apjjears to be a very distinct species. Its large cirri with 

 numerous segments resemble those of *S'. arachnoides: but the centrodorsal is 

 very much larger and the columns of cirrus sockets are segregated into widely 

 separated pairs instead of being closely crowded ; the ossicles of the calyx and 

 arm bases also lack the spinous edges and the high median carinate processes so 

 characteristic of that form. The small centrodorsal of 8. spinicirra, which is 

 hemispherical or bluntly conical with no differentiation into areas, as m'cII as the 

 short cirri with few segments, each of which bears a spine, at once differentiate 

 that species. S. acutiradia has also a very small centrodorsal with only about 

 fifteen cirrus sockets which do not appear to be grouped in any way. S. brevi- 

 radia lias cirri with from forty to fifty segments, " or afewmore"; but the centro- 

 dorsal is of the type found in *S. arachnoides, ([uite different from that in the 

 species under consideration. It is probable, however, tliat this is the species to 

 which jS'. carinilcra is most closely allied. 



A smaller specimen found with the type ap})ears to represent a younger 

 stage of the same species. Tlie cirri are about 40 mm. long, and have from 

 54 to 58 segments of wliicli t'.ie sixth is a transition segment; the centrodorsal 

 is truncated conical. 35 mm. in diameter at the base and 1 5 mm. at the dorsal 

 pole, and 3 mm. high, measured along the inclination of the sides; the dorsal 

 pole is covered with short spines ; in general the centrodorsal is as in the other 

 larger specimen, but, owing to its conical shape, the midradial furrows converge 

 distally. The ends of tiie basal rays are rather more prominent than in the 

 other specimen ; the radials are smootli, without t!ie lateral spines ; the IBr, liave 

 scarcely a trace of the eversion of tlieir edges, Itut possess a higher and sliai'pei- 

 median keel, and usually also a sliarp tubercle on (heir distal border about one- 

 thii'd of the distance between the distal lateral angle and the median line. The 



