244 BULLETIN 100, UNITED STATES NATIONAL, MUSEUM. 



(f. Furrow spiues 8 to 10; large radial plates with 2 to 4 central gran- 

 ules bipunctus. 



a'. Superomarginals separated on outer part of ray by a single series of abac- 

 tinal plates, but the last few plates may be in contact medially. 

 b^. Size small ; distal marginals with a small central tubercle ; marginals 



tumid ; furrow spines 4 or 5 mamillatus, p. 247. 



b^. Size large ; distal marginals not tuberculate ; marginals not individually 

 tumid ; furrow spines 8 to 12 symbolicus, p. 253. 



ROSASTER NANNUS Fisher. 



Plate 61, figs. 1, 2 ; plate 68, fig. 6 ; plate 91, figs. 3, 3a. 

 Rosaster nannus Fisher, 1913a, p. 631. 



Diagnosis. — A small species resembling E. conflnis (Koehler), but 

 differing in having larger, hexagonal, radial plates, with differently 

 formed and characteristic marginal granules, fewer furrow spines 

 (4 or 5) and 2 instead of 3 series of subambulacral spines and gran- 

 ules. Disk stellato-pentagonal, the rays at first tapering abruptly 

 to the third superomarginal, which meets its fellow medially, then 

 very gradually, the extremity being blunt and the general form 

 resembling that of Paragonaster; breadth of ray at inner end of third 

 superomarginal equaling first 2^ superomarginals measured on am- 

 bitus ; radial plates large, with large, valvelike granules on the 

 lateral borders, and smaller ones on the transverse margins ; furrow 

 spines 4 or 5; subambulacral armature in 2 longitudinal series, the 

 inner consisting of 3 or 4 spines ; consecutive plates of median radial 

 series joined by 2 internal ossicles, and joined to the adradials by 2 

 transverse ossicles, the former being absent on the adradial series. 

 R=24 mm., r=6.5 mm., R=3.7 r; breadth of ray at midinter- 

 brachium, 7 mm. 



Description. — Abactinal area stellato-pentagonal, bounded by broad 

 superomarginals (2.5 of each series). Plates strongly tabulate, even 

 the few interradial ones being raised as much as is usual for the 

 radial platQS of NympJiaster. Median radial plates, hexagonal, 

 wider than long, with very straight edges. Parallel to this are 

 2 longitudinal series of tabulate plates, the adradial plates being con- 

 spicuously smaller than the radial and the next conspicuously smaller 

 than the adradial. Between this second series and the margin are 

 2 short series of lower interradial plates, forming vvith those of the 

 other side of interbrachium 2 chevrons. A large proximal median 

 radial plate has 15 to 25 central hemispherical slightly spaced gran- 

 ules, gradually decreasing to as fcAV as 2, })ut usually 4 or 5, on the 

 distalmost plates of the series. The peripheral granules are con- 

 spicuously larger on the lateral margins, where the,y are flattened, 

 polygonal, valvelike, and trimmed to conform to the edge of the hex- 

 agon; but they decrease abruptl}- in size toward the middle of the 



