216 HAWAIIAN AND OTHER PACIFIC ECHINI. 



called tridentate by Doderlein, but as they usually have a well-marked articular 

 loop, it seems better to call them ophicephalous. The triphyllous pedicellarise 

 are small and hard to detect but are usually common. The valves are .10-.20 

 mm. in length and quite variable in form, though generally rather wide and 

 truncate at tip (PI. 91, fig. 5). The stalks are, as usual in triphyllous pedicel- 

 larise, much longer than the neck, which is several times as long as the head. 



The sphceridia (PI. 1 , figs. 13, 22) as in the Centrechinidse, are present on the 

 lower secondary element of the ambulacral plates, at the inner side of the foot, 

 from the peristome nearly to the ocular plate. They do not exhibit great variety 

 of form or possess any distinctive characters. 



The calcareous spicules (PI. 91, fig. 21) are large, fenestrated plates, of very 

 diverse forms and sizes. The surface may be smooth or provided with a few, 

 or with numerous spinelets. Such deposits are obviously very different from 

 the normally triradiate spicules of the Centrechinidse. 



QENOPEDINA. 



A. Agassiz, 1869. Bull. M. C. Z., I, p. 256. 

 Type-species, Ccmopedina cubensis A. Agassiz, 1. c. 



Careful comparative study of the material available, and of the descrip- 

 tions and figures of de Meijere, Doderlein, and Mortensen shows that there 

 are now known five species of this genus. They are distinguished from each 

 other most satisfactorily, by the characters found in the abactinal system, the 

 primary spines, and the coloration. The species of the West Indian region 

 (cubensis A. Ag.) has been longest known and is the type of the genus; the 

 specimens before us are all small, but Koehler has been so fortunate as to have 

 some very fine material from depths of 605-660 fathoms in the eastern North 

 Atlantic and his beautiful colored figure (1909, Ech. "Princesse Alice," PI. 1, fig. 

 1) well shows the appearance of this interesting species. The Japanese form 

 (mirabilis Dod.) was the next to be discovered and the "Albatross" collection 

 fortunately supplies sufficient material for a satisfactory understanding of that 

 species. The "Siboga" collected specimens of a Cgenopedina near the Kei 

 Islands, which was regarded by de Meijere as undescribed and to which he gave 

 the name indica. Doderlein (1906, "Valdivia" Ech., p. 176) has expressed the 

 opinion that this is only a variety of mirabilis but I am not able to agree with 

 him. The two forms seem to be quite distinct. In 1907 (Bull. M. C. Z., L, 

 p. 245) de Meijere's species was recorded from the Hawaiian Islands but a more 



