SUB-CLASS I 



ASTEROIDEA ENCRINASTERLE 



207 



Aspidosvi)inpet(il(riiles,$\iii(>n. Lower Devonian ; vicinity 

 f Niederlahnstein, Nassau. ,4, Ventral aspect, natural size. 



Sub-Class 1. ENCRINASTERIAE. Bronn. 



Palaeozoic Star-fishes with hit slightly inclined ambulacral ossicles, their ends 



meeting alternately in the middle of 



the ambulacral grooves. Madreporite 



situated on the oral &!' <>f the disk. 



Cambrian to Carboniferous. 



Two principal groups may be 



indicated in this sub-class, in one 



of which marginal plates are 



strongly developed, and in the 



other they are either absent or 



rudimentary. So little is known, 



however, of the complete structure 



of the majority of Palaeozoic forms, 



that in the case of some genera it 



is impossible as yet to determine 



positively the group in which they 



should be classed. 



To the first group belong the 



following genera : Aspidosoma, 



Goldf. (Fig. 337). Devonian ; Rhenish Prussia. Palaeaster, Hall (Petraster, 



Billings ; Archasterias, 

 Miiller), (Fig. 338). Ordo- 

 vician to Carboniferous ; 

 Europe and North America. 

 Salteraster, Stiirtz (Palae- 

 aster,~~!3aTter, p.p.) Ordo- 

 vician ; England. Palaeo- 

 stella, Stiirtz. Lower De- 

 vonian ; Bundenbach. 



Palasterina, M'Coy 

 (Cambrian to Devonian ;. 

 Europe and North America), 

 should probably be ranked 

 in this group as a transitional 

 form. Ur aster ella, M'Coy 

 (Stenaster, Billings, p.p.), 

 (Ordovician ; Canada), is 



Palaeaster Eucharis, Hall. Devonian ; Hamilton, New York, also Considered by Stiirtz as 

 A, Ventral aspect, natural size. If, Dorsal surface of one of the arms. mprnhpr nf r Viic crrnnn 

 C, Diagrammatic view of ventral surface of the arms (after Hall). lb 8 1 OU P- 



To the second group 



belong the genera : Palaeocoma, Bdellacoma, and fihopalocoma, Salter. 



Silurian ; England. Loriolaster, Cheiropteraster, and Palasteriscus, Stiirtz. 

 Lower Devonian ; Bundenbach. 



