260 BULLETIN 76, UNITED STATES NATIONAL. MUSEUM. 



d'. Papular areas very large containing upward to sixty papulae; spines large, isolated; 

 no small spine in furrow; madreporic body "euplacote,'' an indei>ondent skeletal 

 piece; skin covering the wide inoahod skeleton, thick; two adambulacral spines; 



rays short and swollen Poraniopsis Perrier, p. 200. 



d^. A small spine in furrow; madreporic body "pseudoplacote" (=the primary inter- 

 radial or basal plate); meshes of skeleton smaller, and rays frequently long and 

 slender. 



f'. No intermari^inal or actinal papulas Echinaster MiiUer and Troschel. 



(■-. Intermargiual and sometimes also actinal papulae Othilia Gray. 



b-. Adambulacral spines arranged in two longitudinal series, but no spinelet deep in furrow; 

 abactiual plates forming wide-meshed network. 

 c'. Adambulacral spines in two longitudinal combs of four or five each, disposed in a double 

 longitudinal series along ray. Abactinal plates bearing compact groups of short equal 



upright spinelets imbedded in a membranous mass Plectaster Sladen. 



c'-'. Adambulacral spinelets not in combs. 

 d'. One furrow, one actinal spine; actinal intermediate spines; inferomarginal spines 



single; abactinal spines generally single and large Poraniopsis Perrier, p. 260. 



(f. Two or three furrow spines; one much larger sometimes bi- or trilobed ligulate spine just 

 behind them; inferomarginal spines three to five, borne on a horizontal lamina; 



abactinal plates bearing single spines or groups of two or three 



Didy aster Alcock and Wood-Mason. 

 d'. Abactinal and lateral skeleton composed of quadrilateral plates united at their angles by 

 imbrication. Four adambulacral spinelets along aboral edge of plate; rudimentary spine- 

 let within furrow; actinal intermediate and inferomarginal plates with three or four aboral 

 spines; dorsal surface mlh very small, short, blunt spines forming irregular longitudinal 

 and transverse rows borne upon edges of plates; ventral and lateral plates connected by 

 an intermediate ossicle; intermediate ossicles occasionally occur between the other plates 

 of skeleton Thyraster Ives." 



Genus PORANIOPSIS Perrier. 



Poraniopsis Perrier, Compt. rend., vol. 106, 1888, p. 703 (nomen nudum); Mission scientif. 

 Cap Horn, III, Stell^rides, 1891, p. 105, pi. 10, fig. 2a, 26. Type, P. echinaster Perrier (erro- 

 neously P. echinasteroides on plate. Bay of Nassau, 95 meters). — Fisher, Zool. Anz., vol. 35, 

 March 29, 1910, p. 568. 



Lahillea de Loriol, Notes pour ser\'ir h. I'^tude des Echinodermes, s^r. 2, fasc. 2, 1904, p. 32, pi. 3, 

 fig. 1, lo-l^. Type, L. mira P. de Loriol (Gulf of San Mathias, Argentina, low tide). 



Alexandraster Ludwig, Mem. Mus. Comp. Zool., vol. 32, July 17, 1905, p. 210, pi. 15, fig.^. 79, 80; 

 pi. 31, figs. 181-183; pi. 32, fig. 184. Type, A. minis Ludwig (Gulf of Panama, 458 fathoms). 



Orlmxinnia de Loriol, Revue critique de pal^ozoologie, Paris, vol. 10, Jan. 1906, p. 78. Proposed 

 to replace Lahillea preoccupied. — Bather, Revue critique de paleozoologie, Paris, vol. 10, 

 1906, p. 131. 



Lahillia de Loriol, Revue critique de paleozoologie, Paris, vol. 10, 1906, p. 77. 



Diagnosis. — Ecliinasteridtie with wide-meshed, reticulate skeleton bearing at the 

 nodes, upright prominent single spines; with large abactinal and intermargmal 

 papular areas (no actinal areas) ; vnth. two adambulacral spines, but none in furrow 

 (as in Uenrida and Echinaster) ; whole body overlaid wth rather tliick skin, mount- 

 ing the bases of spines, and sometimes investing them ; no pedicellaria^ ; madreporic 

 body an independent plate ("euplacote," Ludwig); tube feet with strong sucking 

 disks and single arapullte. 



" Thyraster Ives, type Ediinaster serpentariits Milller and Troschel. Echinoderms from the northern 

 coast of Yucatan and the harbor of Vera Cruz. Proc. Acad. Nat. Sci. Phila., 1890, p. 329, pi. 8, figs. 19, 

 20, 21. 



