8 BLTLLETIN 84, UNITED STATES NATIONAL MUSEUM. 



I give here (pi. 18, figs. 2 and 6) two photographs representing the upper and 

 under faces of the new species, and, for comparison, a photograph of the under face 

 of 0. elaps (fig. 4) ; the iipper face of the disk and a side view of the arms of the hatter 

 species are represented on plate 1, figs. 1 and 2. 



The new species being fairly near to 0. elaps, it ■will be sufficient to indicate 

 here the differences which separate them. 



The diameter of the disk is 29 mm. and the largest arm is 142 mm. long. 



The notches of the upper face of the disk of 0. dypeata, at the beginning of the 

 arms, are less strongly marked than in 0. elaps; they do not reach beyond the second 

 upper brachial plate, and, moreover, the first of these two plates is extremely short 

 and rudimental; it may even be completely lacking; while in 0. elaps, the notch 

 extends at least as.far as the middle of the third upper bracliial plate. The shape 

 of the upper brachial plates is the same in both species, but the under plates of 

 0. ehjpeata are very much widened, and they are much wider than long, with a 

 convex distal edge and rounded sides, while in 0. elaps, these plates are almost 

 square, nearly as wide as long, and the lateral edges remain straight; they jom the 

 distal side by a rounded angle only. 



The number of the brachial spines is always inferior by one unit to that observed 

 in 0. elaps as it has been indicated by Lyman. This number, which is seven at the 

 base of the arms, afterwards decreases to six. Excepting the first ventral spine, 

 which is more developed, all these spines are almost as long as the article and they 

 are clearly more elongated than in 0. elaps; consequently, the difference between 

 the length of the first ventral spine and that of the following spines is not so strongly 

 marked as in the latter species; in return, this first ventral spine is a Httle more 

 widened here. 



Lastly, the shape of the mouth shields is altogether different in the two species. 

 Instead of being triangular, as long as wide, with a rounded apex, a convex distal 

 edge and very wideh' rounded lateral angles, these shields are rather quadrangidar: 

 they are somewhat longer than wide and their distal side, which is very clearly 

 excavated, joins the lateral edges in angles which are more open and much more 

 broadly rounded than in 0. elaps. These lateral edges are hardly convergent and 

 they are united by a very convex proximal edge, but they do not join in an angle, 

 as is the case for this latter species. The shield which carries the madreporic pore 

 is more particularly elongated and it is one-and-a-half times longer than wide. 



The sum of these characters seems important enough to account for a specific 

 separation for this Ophioderma, which perhaps does not abandon a certain depth. 



OPmODERMA, species ?, young. 

 Plate 2, figs. 1-2, 



Green Cay, Bahamas. One specimen (Ace. No. 41471). 



I can not specifically determine a Yerj young specimen which evidently belongs 

 to the genus Ophioderma, the diameter of the disk of which does not exceed 4.5 mm., 

 wliile its arms reach only 10 mm. This example is remarkable, owing to the fact 

 that the various parts of the body are almost entirely covered Math very numerous 

 granules which appear on certain plates or plate-parts which ought to be bare in 



