172 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



LUIDU AVICLLAKIA Fisher. 



Plate 43, fig. 1; plate 44, fig. 2 (see also plate 44, fig. 3, L. moroisoana) ; 



plate 46, figs. 2, 2a-c. 



Luidia avicularia Fisher, 1913c, p. 203. 



Diagnosis. — Very closely related to L. Integra Koehler, which it 

 resembles in general appearance but from which it differs in the 

 following particulars: Scattered spinopaxillae among the normal 

 paxillae of the 3 dorsolateral series; siiperomarginal and abactinal 

 paxillae with small two- jawed pedicellariae ; central spinelets of 

 superomarginal and abactinal paxillae, sharp, longer than thick, not 

 granuliform ; inferomarginals encroaching conspicuously upon abac- 

 tinal area and with marginal spines varying from 2 to 6; infero- 

 marginal pedicellariae present on some of the plates; the character- 

 istic furrow pedicellariae, proximally with dorsal jaw curved over 

 end of the slightly curved ventral jaw: proximal adambulacral plates 

 with generally more than 3 spines, and more than 1 subambulacral 

 pedicellaria, pedicellariae sometimes replacing the spines; gener- 

 ally 2 large dental pedicellariae, directed over the peristome. Kays 

 10. E=195 mm., r=18 mm., R=10.5 r; a shorter ray, E=1T5 mm.; 

 breadth of ray at base, 13 mm. ; breadth 15 mm. from base, at widest 

 part, IT to 18 mm. Eay gradually tapering, blunt, abactinal surface 

 slightly convex. 



Description. — The most important abactinal feature in which avi- 

 cularia differs from Integra is in the presence of relatively few, 

 central, sharp spines (smaller than those of the superomarginal 

 plates) on the 3 dorsolateral regular rows of paxillae, the rather 

 more rounded contour of the latter, and the presence on many of the 

 paxillae (both superomarginal and abactinal) of a small two- jawed, 

 spiniform pedicellaria. On the abactinal plates the pedicellaria is 

 generally marginal and about as long as the peripheral spinelets. 

 On the superomarginal paxillae (where 2 pedicellariae are occa- 

 sionally present) it frequently is found at the outer adoral corner, 

 or near the proximal rather than the distal transverse margin. 

 The armature of the center of the tabulum consists of upward of 

 15 sharp, short spinelets (not granules) surrounding, without defi- 

 nite order, the stout, sharp central spinule, which varies in length 

 from a little longer to a little shorter than the width of paxilla 

 crown. The peripheral spinelets are slender and upward of 30. 

 Another (difference, rather striking, but possibly not constant, is the 

 fact that when viewed from above the inferomarginals form a broad 

 border to the abactinal area, often equaling the combined width of 

 the 2 adjacent series of paxillae. I am inclined to think this is 

 constant and due to the more arched inferomarginals. The upper 

 end of the inferomarginals, judging by Koehler's photographic fig- 

 ures, are not at all conspicuous in Integra. 



