OPHIUROIDEA. 



259 



supposed to be confined to this period and to be character- 

 istic of the Muschelkalk. In the Jurassic and Cretaceous 

 periods, as in the Tertiary, remains of Ophiuroids are by no 

 means very uncommon, and they are generally referred 

 partly to extinct types (such as Acroura). Most of them, 

 however, are apparently referable to well-known existing 

 genera, such as Ophioderma (fig. 146), Ophiocoma ( = Ophi- 

 urella), OpMoylyplia (- Ophiura, Forbes), Ophiolepis, and 

 Amphiura. 



