198 NATURAL HISTORY BULLETIN 



except on the distal third of the rays, bears a small, movable^ 

 tapered, acute spine at the upper angle ; those at the base of the 

 rays are longer than the rest. 



Some of the inferomarginal plates of the rays have a similar^ 

 but smaller, spine at the lower angle and near the distal edge of 

 the plate; most of the interradials have also a small cluster of 

 minute granules near the lower end. All the marginal plates 

 are bordered by a very regular and even series of small spinules 

 webbed together to their tips. Those of the upper plates are 

 much more numerous, finer and closer, and more evenly pectin- 

 ate; they nearly touch across the grooves. Those of the lower 

 plates stand a little apart and are more divergent, about half as 

 many in the same space as on the upper plates, and very similar 

 to those between the actinal plates. 



The actinal areas are not large and extend to about the eighth 

 adambulacral. The median odd series consists of two closely 

 united rows of about six each, the distal ones becoming very 

 small. The next series contains a row of five plates and one of 

 three similar plates; this series corresponds to the second and 

 third adambulacrals. 



The adambulacral plates are broad and roundish, the proximal 

 ones quite oblique; their furrow-edge projects over the furrow 

 and bears a row of 10 to 12 small, slender, acute spinules, which 

 are somewhat divergent and webbed together for about half 

 their length; they meet or interlock across the furrow, leaving 

 rounded or ovate open spaces between them for the passage of the 

 large and tapered ambulacral feet. On the outer and lateral 

 margins of the plates there is also a series of divergent, w^ebbed, 

 fasciolated spinules like those of the actinal plates. 



The madreporic plate is rather large, with fine gyri. The 

 dorsal nephridial pore is situated in the center of a low elevation 

 composed of very small, round paxillae. 



Taken by the Albatross at station 2401, in the Gulf of Mexico, 

 in 142 fathoms. (No. 18,428, U. S. Nat. Mus.) 



For more details see the original description. 



Family Luidiid^ Yerrill. 



Luidiidw Verrill, Trans. Conn. Acad., x, p. 201, 1899. Fisher, op. cit., 



1911??, p. 105. Verrill, op. eit., p. 333, 1914a. 

 LuidnncB (subfamily) Sladen, op. cit., pp. 175, 244, 1889. 



