CLASSIFICATION. 43 



17. Metrodira, Gr. — Slightly granular; rays slender, with large single pores and small 



scattered spines on the back ; smooth, and formed of regular, flat ossicula on the 

 sides. M. subulata, Gr. 



18. Rhopia, Gr. — SfcUonia, Ag. Ambulacral spines long, with several series of larger 



spines near them. B. seposita, Retz. 



19. Ferdina, Gr. — Body flat; rays broad, convex and warty above, flat and uniform 



beneath ; ambulacral spines short, united at the base. F.Jlavescens, Leach. 



20. Dactylosaster, Gr. — Rays cylindrical, nearly smooth, formed of regular oblong 



ossicula, each furnished with a central group of unequal, short, mobile tubercles ; 

 one dorsal wart. D. cylindricus, Lamk. 



21. Tamaria, Gr. — Rays cylindrical, formed of seven series of granular, convex, roundish 



ossicula, each of the upper ones with three or four unequal, and the lower ones 

 with a central, short, blunt spine. T.fusca, Gr. 



22. CisTiNA, Gr. — Rays cylindrical, nearly smooth, formed of rows of three-lobed flat 



ossicula, each furnished with a central, mobile spine ; one or two oblong dorsal 

 warts. C. Columbice, Gr, 



23. Ophidiaster, Ag. — Rays cylindrical, elongate, uniformly granular all over, without 



any spines ; back with a small central group of larger tubercles ; dorsal wart 

 concave, with radiating or twisting grooves, 0. aurantius. 



24. LiNCKiA, Nardo. — L. iypus, Nar. ; P. miliaris, Linck., Stel. Mar., t. 28, fig. 47. 



25. Fromia, Gr. — Rays from five to eight, flat, triangular, formed of flat-topped, 



granular tubercles. F. millepora. Lam., Seba. Thesaui'., t. 8,/. a. h. 



26. GoMOPHiA, Gr. — Rays elongate, cylindrical, tapering, with a terminal tubercle ; 



back with large rounded tubercles ; back of the rays with a series of large, conical, 

 convex, tubercular spines ; the spines near the ambulacra small, crowded. 

 G. EgyptiacUy Gr. 



27. Nardoa, Gr. — Rays cylindrical, spineless, formed of large, granular, convex ossicula. 



P. variolatus, Linck., Stel. Mar., t. 8, fig. 10. 



28. Narcissia, Gr.— Body pyramidal, thin, coriaceous, uniformly granular; rays 



tapering, elongate, triangular at the base, formed of thin, flattened ossicula. 

 N. Teneriffce, Gr. 



