336 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



small specimen (the diameter of the disk is 11 mm.), these pores 

 also have the same arrangement, but they are very much smaller 

 than in 0. mauritiensis and very much less evident. 



The presence of ventral pores, a feature concerning which most 

 authors have said nothing, must be considered as one of the essential 

 characters of the genus Ophiarachna. Usually there are two pairs 

 only at the base of the arms; this figure is sometimes exceeded in 

 0. affinis, while in O. incrassata the number of successive pairs is 

 very much higher. 



An opportunity presenting itself of including a photograph of the 

 ventral surface of 0. incrassata for comparison with the new species, 

 I have seen fit to profit by it in reproducing also a photograph of 

 the dorsal surface of the same specimen (pi. 4, fig. 7). H. L. Clark 

 ('08, p. 298), in mentioning the coloration of a specimen from 

 Amboina which he had been able to study, says that the markings 

 of this species conform to the description of Miiller and Troschel 

 " disk greenish, center and areas over radial shields light brownish 

 (not in marked contrast) spotted with yellow; arms reddish buff; 

 arms spines light yellow," etc. 



This type of coloration is different from that which Herklots has 

 shown. I have been able to determine that the Siboga individuals 

 had markings quite comparable to those which Herklots has repro- 

 duced in his colored plate ('68, pi. 6), and I mentioned this fact in 

 1905. The photograph which I include of a Siboga specimen can not, 

 of course, show the coloration, but it indicates the arrangement of 

 the spots on the two surfaces of the disk. The general color of the 

 individual is a slightly yellowish green, a little lighter on the ventral 

 surface; the spots, surrounded by a dark-brown circle, which occur 

 on the dorsal surface are slightly lighter than the rest of that sur- 

 face and of a more yellowish color ; the light-yellow spines show one 

 or two darker rings only at their base. 



In its external appearance and in the very fine granulation of the 

 disk, which is studded with dark spots, O. quinquespinosa shows a 

 resemblance, though a rather vague and quite superficial one, with 

 Ophiocoma doderleini^ which I have already discussed. The length 

 of the spines and the arrangement of the two tentacle scales accen- 

 tuates the resemblance with an Ophiocoma. But aside from the two 

 pairs of pores which occur at the base of the arms, there could be no 

 question of assigning to the genus Ophiocoma an ophiuran which 

 does not possess that vertical clump of tooth papillae so characteristic 

 of the latter genus. If I speak of this purely external resemblance, 

 it is especially for the purpose of calling to mind an error made by 

 Lyman which was noticed by Loriol and more recently by H. L. Clark 

 ('09, p. 113). In the diagnosis which he gives of the genus Ophia- 



