ECHINOIDEA. I. 



63 



simply leaf-shaped, with a little developed net of meshes. The stalk of the pedicellariæ irregularly 

 perforated. 



Species: EcJi. temtc (A. Ag.), uraiins (Wyv. Thomson). 



Distribution: The Pacific, the northern Atlantic. — Ab3-ssal forms. 



Asthenosoma Grube (emend.). 



Synonym: Cyanosonia Sarasin. 



The primary spines on the actinal side curved, with a rather long, narrow hoof; rather great 

 difference betvveen the abactinal and the actinal sides, on account of the numerous primary spines 

 covering the whole actinal side; the areoles are almost of equal size on both sides. The spines on the 

 abactinal side inclosed by a thick, annularly constricted bag of skin. The tube feet form three dense 

 series; the spicules small branched bodies, arranged in longitudinal series. Sucking disk well devel- 

 oped. Only trideutate and triph\llous pedicellariæ. The tridentate ones occur in three distinct forms. 

 The largest form has a long, narrow blade, widened in the point where it is coarsely serrate (not 

 observed in all the species); the second form has a short, broad, and flat blade filled by a rich net of 

 meshes and with coarsely sinuate edge. The third form is simph- leaf-shaped, with the apophysis con- 

 tinued to the middle of the blade, or quite to the point as a sharp, serrate crest. The stalk irregularly 

 perforated. 



Species: ^istli. varium Grube, Gntbci K. ^^g., tcrnis Sarasin, hctcractis Bedford. 



Distribution: Ceylon, the East-Indian Archipelago. — Littoral forms. 



Calveria Wyv. Thomson (emend.). 



The primary spines on the actinal side curved, ending in a little hoof; only a slight difference 

 between the actinal and the abactinal sides. The areoles rather small. The primary spines form a 

 rather conspicuous series aloug the outer margin of the interambulacral areas, especially towards the 

 ambitus on the actinal side. The tube feet in three dense series; the spicules in the outer part of the 

 tube foot larger feuestrated piates, in the lower part smaller and arranged in longitudinal series. 

 Sucking disk developed. Oul}- tridentate and triph>llous pedicellariæ. In the large form of tridentate 

 pedicellariæ the blade is much involuted, only at the point a little widened, and the edge of this 

 widened part is irregularly serrate. The smaller tridentate pedicellariæ chiefly of the same form, only 

 the widened part of the blade comparatively larger, the involuted part smaller. The stalk irregularly 

 perforated. 



Species: C. Iiystrix Wyv. Thomson, gracilis (A. Agass.). 



Distribution: The northern Atlantic, the Philippiues. — Archibenthal forms. 



Aræosoma n. g. 

 The primary spines on the actinal side curved, ending in a little hoof; only a slight difference 

 between the actinal and the abactinal sides; the areoles rather small. The primary spines form a 

 rather conspicuous series aloug the outer margin of the interambulacral areas, especially on the actinal 

 side towards the ambitus. The tube feet in three dense series. The spicules larger fenestrated piates, 

 in the lower part of the tube foot smaller, sometimes irregular needles, more or less distinctly arranged 

 in longitudinal series. Sucking disk well developed. Besides the commonly occurring tridentate and 



