292 



ECHINODERMATA— ECHINOZOA 



PHYLUM IV 



CoUyrites Desm. (Fig. 412). Test ovoid, tumid, more or less truncated 

 posteriorly. Amh disjunct, the anterior one sometimes in a slight groove. 

 Width of the Amb increasing towards the ambitus ; pore-pairs in low primary 

 plates. Periproct posterior, supra-marginal, placed in a groove. Apical 

 system elongate, separated by numerous small plates belonging to the 

 postero-lateral lAmh. Very abundant in the Middle and Upper Jura and 

 Cretaceous. 



Dysaster Ag. Difl^ers from CoUyrites in details of the aj)ical system, the 

 genitals not being separated by the antero-lateral ocular plates. Upper Jura 

 and Lower Cretaceous. 



Hyhodypeus Agassiz (Fig. 413). Jura. Tnfradypeus Gauthier. Upper 

 Cretaceous. Grasia Mich, Jura. 



Hyioclyijeus gibberulus Ag 



Fk;. 41 



Middle Jura ; Soleure, Switzerland. A, B, Dorsal and ventral views. 

 C, Profile. D, Apical system, enlarged. 



Metaporhinus Mich. Test very tall, slightly longer than broad, sub-cordi- 

 form, projecting upwards anteriorly, grooved and oblique behind. Anterior 

 Amh in a groove, with small, simple, distant pairs of pores ; the other Amh 

 flexuous, with comma-shaped pores placed obliquely to one another. Periproct 

 supra-marginal. Upper Jura and Lower Cretaceous. 



Tribe B. SPATANGOIDEA Duncan. 



Peristome eccentric in front, rarely i^entagonal in the adult, usiially with a 

 posterior lahrum, behind which is a long plastron bounded laterally hy the posterior 

 ambulacra. Ambulacra dissimilar. Inferamhidacra with a single plate at the 

 peristomal margin; the postero-lateral areas usually unsymmetrical actinally. 

 Fascioles piresent or absent. 



. Family 4. Ananchytidae Desor. 



Test ovoid or suh-cordiform in marginal outline, tall or depressed, and with large 

 plates. Ambulacra in a bivium and trivium, nearly similar, flush, apetalous ; pore- 

 pairs largest near the apex and at the peristome, may be uniporous. Periproct 

 variable in position. Cretaceous to Eecent. 



Ananchytes Lam. {Echinocorys Breyn.) (Fig. 414). Test large, oval in marginal 

 outline ; high, rounded or keeled apically, flat actinally. Amb biporous, the 

 pore-pairs well developed abactinally, but becoming smaller, closer and 



