WEST INDIAN STARFISHES 199 



Disk small, covered with true paxillae, which are usually largest 

 at the sides of disk and rays ; rays five to ten or more, long, flat, 

 flexible in life. Superomarginal plates small, paxilliform, often 

 indistinguishable from the dorsal paxillse. Inferomarginals 

 transversely elongated, large, spinose, fascioled, corresponding 

 in number and radial length with the adambulacrals and sep- 

 arated from them throughout the rays by a row of small per- 

 actinal plates. 



Pedicellarise usually present on the aetinal side, forceps-like, 

 with two or three blades, or spinifonn. 



Ambulacral feet large, flattened, muscular; can be used as 

 paddles for gliding rapidly along the bottom just under the sur- 

 face of sand or mud. I have observed (1901) that Luidia clath- 

 rata swims or paddles with remarkable speed, just under the sur- 

 face of the sand in shallow water, and that it swims or glides 

 actively in an aquarium, by using its feet as paddles. 



The dorsal nephridial glands, or ''coecal appendages," in- 

 testine and dorsal pore are lacking. The papulae are branched. 



This family is very distinct from all others, but nearest to 

 Astropectinidce. It is well represented in the West Indies, as in 

 most tropical and subtropical seas. 



Genus Luidia Forbes. 



Luidia Forbes, Wern. Trans., 1839, i^. 14; Mem. Wern. Soc, viii, p. 128, 

 1840. Miiller and Trosehel, Syst. Aster., p. 77, 1842. Sladen, op. cit., 

 p. 244, 1887. Fisher, 1911b, p. 105. Verrill, op. cit., p. 334, 1914a. 



Rays five to ten, rather flat, flexible. Dorsal columnar paxillae 

 have lobate, articulated bases; summits either plainly paxillose 

 or with a central spine or tubercle (spinopaxill^e), or with both 

 kinds; largest next the lateral borders of the rays. Inferomar- 

 ginal plates spinose and spinulose. Pedieellariae often absent; 

 when present, forceps-like, with two or three blades or valves. 

 They are usually situated on the adambulacral plates ; sometimes 

 on the inferomarginals or peractinals. 



Inferomarginal plates are transversely elongated, with wide 

 and deep fasciolated grooves between them, bordered by slender 

 spinules ; central portion with one or more rows of spines. Su- 

 peromarginals small, paxilliform, rounded. Adambulacral plates 

 short, with one furrow-spine (rarely two) ; they are separated 



