280 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



differs in having proximally narrower rays, differently formed su- 

 peromarginals, which on disk extend laterally beyond the infero- 

 marginals (not the reverse), in having coarser granules, larger 

 primary basal plates, shorter furrow spines, especially the middle 

 members, and fewer oral spines, the series of which is not incurved. 

 The inferomarginal plates are narrower and more bandlike, on the 

 ray and the superomarginals are much more numerous. Nymphaster 

 nora Alcock has still longer rays (R=6.3 r) very narrow infero- 

 marginals in the interbrachia, 12 furrow spines and 3 plates sur- 

 rounding the madreporite. In the form of the marginal plates 

 arthrocnemis closely resembles nora. 



NYMPHASTER MESERES Fisher. 



Plate 66, fig. 2; plate 67, fig. 2; plate 68, fig. 2; plate 69, fig. 2; plate 92, 



figs. 4, 4a. 



Nymphnster meseres Fisher, 1913ff, p. 639. 



Diagnosis. — Similar in proportions and general form to ^V. arthro- 

 cnemis but marginal plates not tumid (although ray is sharply 

 4-angled) and dorsal surface is subplane; sixth and sometimes fifth 

 superomarginal longer than width of dorsal surface (tenth in 

 arthrocnemis) ; third inferomarginal longer than width of its actinal 

 surface; superomarginal and inferomarginal 2-jawed slender pedicel- 

 lariae regularly present. Width of ray at proximal end of first pair 

 of superomarginals which meet medially equaling first 3.5 to 3.66 

 superomargijials measured along ambitus; radial abactinal plates 

 hexagonal to roundish; oral spines 9 to 11; furrow spines increasing 

 from 5 or 6 to 10, 11, and 12 far along ray. R=about 60 mm., r=17 

 mm., R=3.6 rdr ; breadth of ray at midinterbrachium, 19 mm. 



Description. — The abactinal plates are similar to those of arthro- 

 cnemis. but the primary apicals are smaller, being subequal to the 

 largest radial paxillae, which have 8 or 10 central and 12 to 15 periph- 

 eral granules. The papular areas seem to be relatively a little wider 

 in meseres^ although the specimen is much smaller; 7 longitudinal 

 rows are included in the papular areas, with a few plates of 2 addi- 

 tional rows on some radii. 



One of the main differences is in the shape of the superomarginal 

 plates which are like rectangular blocks with plane (not tumid) 

 facets. The sutural line along side of ray is a trifle sunken, as also 

 that of the midradial line on outer part of ray. The plates are 

 sharply oblique in the midinterbrachia and the width decreases more 

 rapidly over the length than in arthrocnemis .^ as indicated in diag- 

 nosis. Granules depressed hemispherical, rather coarse, and touch- 

 ing one another, not spaced as in hdbrotatus and atopus. Marginal 

 pedicellariae few, slender, in the interbrachia. Terminal plate (of 



