ECHINODERMATA— ECHINOZOA 



PHYLUM IV 



petaloid pärts conjugated, the outer ones usually the largest. Peripetalous 

 fasciole present. 



Subgenus Tripylus Pliill. {Ahatus Troschel). Recent. 



Faorina Gray. Recent. Pericosmus Ag. Cretaceous and Tertiary. 

 Linthia Merian (Besoria Gray) (Fig. 419). Anterior Amb in a deep 

 groove, the pores round and small, in pairs on either side. Antero-lateral 

 Ami) longer and more divergent than the others, with petals sunk in grooves. 

 Pores conjugated. A peripetalous and lateral fasciole present. Cretaceous 

 to Recent. 



Schizaster Ag. (Figs. 420, 421). Resembling Linthia, but the apical System 

 is posteriorly eccentric, and the Amb very diverse. 

 Tertiary and Eecent. 



Prenaster Desor; Ornithaster and Coraster Cotteau. 

 Eocene. 



Agassizia Val. ; Moira A. Ag. Tertiary and Recent. 

 Hs A. Ag. Recent. 



Fig. 420. 



Schizaster arcMaci Gott. 

 Eocene ; San Giovanni Ila- 

 rione, near Vicenza. 



Fig. 421. 



Schizaster fragilis Ag. Apical Sys- 

 tem, greatly enlarged (after Loven). 



i« Fig. 422. 



Micraster coranganius 

 (Ijam.). Apical System. 



Section C. Prymnodesmia. Subanal fasciole present. 



Micraster Ag. (Figs. 422, 423). Test cordiform, tumid, rather depressed. 

 Anterior Amb apetaloid, in a shallow depression ; antero-lateral Amb sub- 

 petaloid dorsally, diverging ; postero-lateral shorter than the others, with 



Fin. 423. 

 Micraster cortestiulinarius Goldf. White Chalk ; Meudon, near Paris. Natural size. 



