GENOCIDARIS APODA. 297 



doubt a primitive character, is combined with a perfectly naked buccal 

 membrane, a specialized feature, and quite specialized globiferous pedi- 

 cellarise; an unusual combination which makes the genus easy to recognize. 

 The species originally described from the West Indies (maculata) is now known 

 from the eastern Atlantic and from the Mediterranean, according to Mortensen 

 and Koehler. A second species (decipiens) was collected by the "Siboga" at 

 Saleyer, Flores and Sumbawa, D. E. L, in shallow water. De Meijere's descrip- 

 tion of the abactinal system of this species would lead one to suppose that the 

 arrangement of the plates is very similar to that which is characteristic of Gym- 

 nechinus. Examination of two specimens, received from the Amsterdam 

 Museum, shows that the periproct is not noticeably excentric, but that the anus 

 is crowded far to the right by the huge suranal plate. Genital 1 is rather low 

 and genital 3 rather high but there is nothing like the disproportion shown in 

 Gymnechinus. None of the ocular plates reach the periproct but I and II are 

 appreciably nearer than the others, which suggests the condition of Gymnechinus. 

 Owing to the deep sculpturing of the plates, it is not easy to make out the sutures 

 and de Meijere was probably either misled in supposing two oculars to be insert 

 or else the specimen on which his statement is based, was exceptional. That it 

 is not a question of size is evident from the fact that his largest specimen was 

 only seven millimeters h. d. while our larger one is over six. Comparison with 

 the other species of the genus shows that the excentricity of the periproct and 

 of the anus are little if at all greater in decipiens than in the others. The third 

 species (apoda) was taken by the "Albatross" off southern Japan in rather 

 deeper water than that in which its East Indian neighbor was found. The 

 three species may be distinguished from each other as follows : — 



Buccal tube-feet 10, one for each buccal plate. 



Buccal plates large forming a nearly closed ring around mouth maculata. 



Buccal plates small, not forming a ring around mouth, as one plate in each pair is 



decidedly more distal than its fellow decipiens. 



Buccal tube-feet 5, wanting on one buccal plate of each pair apoda. 



Genocidaris apoda A. Ag. and CI. 



Genocidaris apoda A. Agassiz and Clark, 1907. Bull. M. C. Z., LI, p. 126. 



Plates 93, figs. 16, 17; 100, figs. 1-3. 



The largest specimen is 7 mm. in diameter and rather more than 3 mm. high. 

 The abactinal system is well over 4 mm. across while the actinostome is not over 



