SUMMARY. 355 



Genus 18. — Echinobrissus, Breynius (p. 248). 



Test small, oval or subcircular, rounded anteriorly, truncated posteriorly ; base slightly 

 concave, upper surface convex ; plates covered with microscopic granulations, and per- 

 forated tubercles in depressed areas. Ambulacral areas narrowly lanceolate. Oral 

 opening small, excentral, pentagonal, lodged in an excentral depression. Apical disc 

 small, quadrate and compact, composed of four perforated and one imperforate genital 

 plate ; the right antero-lateral supports the madreporiform body. Anal opening oval, 

 in a groove extending from the summit to the margin. Range, from the Inferior Oolite to 

 the existing period. Two British Cretaceous species (pp. 249 — 251). 



19. — Trematopygus, d' Orhigny (p. 252). 



Test thin, ovate, contracted and rounded before, more or less enlarged behind, convex 

 above, concave on under surface. Ambulacral areas subpetaloid above, narrow below. 

 Oral opening irregularly pentagonal, compressed obliquely from left to right, and from 

 above downwards. Apical disc quadrate, excentral, with four perforate ovarial plates, 

 and one imperforate plate. Madreporiform body covering the genital elements, and 

 forming a prominence in the centre of the disc. Oculars very small. Anal opening very 

 large, pyriform elongated above the margin and placed in a groove. One British 

 Cretaceous species (pp. 253, 254). 



Genus 20. — Caratomus, Jgassiz (p. 254). 



Test thin, small, ovoid or circular, rounded before, often rostrated behind ; sides 

 inflated, convex above and below. Ambulacra petaloid on upper surface, straight below. 

 Poriferous zones with simple, equal, non-conjugate pores, disposed in pairs closely 

 approximated at the summit, apart in the middle, and approximated at the ambitus, 

 feebly indicated at base by lines converging around the peristome. Interambulacral 

 zones wide, covered with large tubercles. Oral opening nearly central, always obliquely 

 elongated. Apical disc nearly central, with four perforated ovarials and five oculars, the 

 madreporiform body extending into the middle of the disc. Anal opening inframarginal 

 and not visible from upper surface, transversely oblong or triangular, and sometimes 

 placed in a rostrated development of the single interambulacrum. Genus found in the 

 Cretaceous series of rocks. One British Cretaceous species (pp. 255 — 256). 



