REPORT ON THE ASTEROIDEA. 



245 



ance to the plate in question if my observations had been limited to a single species, but 

 I have detected the presence of the intermediate plate in every species I have examined 

 critically (small and more or less aborted in some cases it is true, but present in all) ; and 

 I can assert its existence in all the forms included in the following synoptic table : — 



Synopsis of the Species included in the Genus Luidia herein described. 



A. Certain paxillae bearing a large central spine on the tabulum. 



a. Rays eight to ten. Spine-hearing paxillae separated from the marginal plates by 



three longitudinal series of plain paxillae. Plain paxillae on the median 

 area of the ray with several papilliform granules on the tabulum, scarcely 

 larger than the encircling series. Infero-marginal plates with five spines 

 gradually increasing in size as they approach the margin of the ray. 

 Often two pedicellariae behind, and forming a serial line with, the spines 

 composing the adambulacral armature aspera. 



b. Rays five. Spine-bearing paxillae separated from the marginal plates by two 



longitudinal series of plain paxillae. Plain paxillaj on the median area 

 of the ray with one large tubercle-like central granule. Infero-marginal 

 plates with the lateral (and sometimes a second spine) much longer than 

 the others. One pedicellaria behind the adambulacral armature, and often 

 absent alternata. 



B. Paxillae without a large central spinelet. 



a. Paxillae with a quadrate tabulum. 



a. Lateral spine very short, compressed and robust. Forficiform pedicellariae 



on the infero-marginal plates. Valvate pedicellariae above the infero- 

 marginal plates .......... limbata. 



b. Lateral spine long, delicate, tapering. No forficiform pedicellariae on the 



infero-marginal plates. No valvate pedicellariae present . . . dathrata. 



b. Paxillae with a stellate crown. 



a. Adambulacral armature forming a single transverse series continuous with 

 the spines on the infero-marginal plates. 

 a. Seven rays. Pedicellariae three-jawed. 



i. One spine on the actinal area of the adambulacral plates, 

 long, robust, cylindrical, sometimes with a small unequal 

 companion. Pedicellariae very large, three-jawed, nut- 

 shaped, very broad at the base, nearly as broad as long. 

 Infero-marginal plates with three or four spines, the 

 outer two or three subequal, the lateral or median one 

 the longest ......... ciliaris. 



/S. Five rays. Pedicellariae two-jawed. 



i. One spine on the actinal area of the adambulacral plates. 

 Pedicellariae long and spine-like. 



1. The actinal spine of the adambulacral armature short, 

 robust, conical. The pedicellariae with delicate 

 spine-like jaws. Infero-marginal plates with three 

 spines, the lateral one long, the other two much 

 smaller, less than the actinal spine of the adambu- 

 lacral armature ....... longispina. 



ii. Two spines on the actinal area of the adambulacral plates. 

 Pedicellariae short and papilliform. 



