GENERA AND GEOTTPS Of THE ECHINOIDEA. 287 



Posterior iuterradium with, a labrum separated from tlie 

 amphisternum ; postero-lateral interradia meeting abactinallj 

 and also actinally. Anterior groove deep and narrow near the 

 actinal margin, not above ; peristome in the bottom of the groove. 

 Periproct in a shallow pouch above the short beak and below the 

 overhanging posterior part of the test. Pasciole absent. 



Recent. South Pacific ; 1600-1950 fms. 



Grenus Echustocrepis, A. Agassiz, 1879, Proc. Amer. Acad. 

 vol. xiv. p. 206 ; 1881, Report on ' Challenger ' Echini, p. 143. 

 Lovtn, 1883, Pourtalesia, p. 82. 



Test large, long, subpyramidal, broadest anteriorly, pointed 

 behind ; apex excentric in front. Marginal outline irregularly 

 triangular, nipped in at the sides, with rounded angles ; margin 

 tumid, with a groove in the anterior part, which is deep and 

 narrow actinally. Actinally flat, with a keel from the end of the 

 anterior groove to the periproct, which is submarginal. Abac- 

 tinally steep in front and sloping gradually posteriorly ; a broad 

 long keel passing backwards and overhanging the periproct. 

 Plates of the test usually large, hexagonal. 



Apical system excentric in front, at the vertex, compact, with 

 four basal plates, three perforated by genital ducts; and the 

 madreporite in the right anterior and extending more or less into 

 the other basals ; sutures obliteiai-ed. The anterior and antero- 

 lateral radial plates aborted ; the postero-Jateral small and in 

 contact behind the postero-lateral basals. 



Ambulacra apetalous, uniporous, flush except where the an- 

 terior is in the groove. 



The postero-lateral and posterior interradia not reaching the 

 peristome ; the long labrum continuous with the sternum and 

 also not entering the peristomial margin ; postero-lateral areas 

 neither uniting dorsally nor actinally. Tentacles homoiopodous. 



Peristome at the bottom of the anterior groove actinally ; the 

 margin formed by the anterior ambulacrum, the antero-lateral 

 interradia, and the antero- and postero-lateral ambulacra. Tu- 

 bercles small and few, one on a plate abactinally, largest on the 

 sternum, much granulation. Spines slender, short and club- 

 ended. Neither a rostrum nor a fasciole. 



Recent. South Pacific ; 1600 fms. 



