442 L. Agassiz on the Echinodermata. 



6. Stellonia, Nardo (Uraster, Ag., MSS. — Pentasterie, De Bl. 

 in part, and his Solasteries) . — Body starlike, entirely covered with 

 more or less prominent spines. 



St. rubens, Nardo (Ast. rub., Linn.). — St.sepitosa, N. (Ast. sepit., Linn.) 

 — St. glacialis, N. (Ast. glac", Linn.) — St. spinosa, N. (Ast. spin., Link.) — 

 St. angulosa, Ag. (Ast. angul., Mull.) — St. endeca, Ag. (Ast. end., Linn.) 

 — St. papposa, Ag. (Ast. pap., Linn.) — St.Helianthus, Ag. (Ast. Hel., Lam.) 

 — St. Echinitis, Ag. (Ast. Echin., Lam.) — Those species in which the num- 

 ber of rays varies from 5 to 7 form the transition to the true Solasterice. The 

 Ast. lanceolata and lumbricalis, Goldf., should probably also be referred to 

 this genus. 



7. Asterina, Nardo (Clenaster, Ag. MSS. — Asterias, sect. C.De 

 Bl. — Pentaceros, Link). — Body pentagonal, covered with pectinated 

 scales ; upper surface inflated ; grooves of the under surface deep. 



A. minuta, N. (Ast. minuta, Linn.) 



8. Palmipes, Link. (Palmaste'rie, De Bl. — Anseropoda, Nardo). — 

 Body pentagonal, very flat, thin, but membranaceous at its edges. 



P. membranaceus, Link. 



9. Culcita, Ag. — Body pentagonal, slit at the angles ; teguments 

 granular. 



C. discoidea, Ag. (Asterias discoid., Lam.) 



II. The Ophiura are distinguished from the Asteria by the central 

 part of their body forming a distinct and flattened disc, to which are 

 annexed more or less elongated and even ramified rays, with no 

 grooves on their under surface. 



1. Ophiura, Lam. and Ag. (Sect. A. De Bl.) — Disc much flat- 

 tened ; rays simple, squamose, bearing very short spines adhering to 

 the rays. 



O. texturata, Lam. — 0. lacertosa, Lam., &c. 



2. Ophiocoma, Ag. (Ophiura, De Bl. sect. B.) — This genus differs 

 from the preceding in having long, very moveable spines attached to 

 the rays. 



O. squamata, Ag. (Ophiura squam., Lam.) — 0. Echinata, Ag. (Ophiur. 

 echin., Lam.), &c. 



3. Ophiurella, Ag. — Disc scarcely distinct. All the species are 

 fossil. 



O. carinata, Ag. (Ophiura'car., Munst.) — 0. speciosa, Ag. (Ophiura spec, 

 Munst.) — 0. Milleri, Ag. (Ophiura Mill., Phil.) — 0. Egertoni, Ag. (Ophi- 

 ura Egertoni, Brod.) 



4. Acroura, Ag., is closely allied to Ophiura, properly so called, 

 but differs in having, instead of the spines, small scales placed on 

 the sides of the rays. The rays themselves are very rough. One 

 fossil species. 



