92 BULLETIN 84, UNITED STATES NATIONAL MUSEUM. 



In most samples from station 2664, the diameter of the disk varies between 

 5 and 6.5 mm., and in that of station 2655 it reaches 7 mm. Almost all the speci- 

 mens have their arms broken, and the length of such as remain whole varies between 

 30 and 35 mm. 



I have been able to ascertain that these specimens are in perfect conformity 

 with the three samples from the dredgings of the Blake, which I mentioned when 

 describing 0. pentacrinus and which were given by Agassiz to the Jardin des Plantes 

 under the name of 0. pentacrinus. These three specimens were evidently deter- 

 mined by Lyman, who had in hand the Ophiurans from the Blake; they are a little 

 smaller than the specimens from the Albatross, the diameter of the disk ranging 

 from 2.8 to 4 mm. All three have their external oral papilla flattened and widened, 

 and the name of 0. pentacrinus can not be applied to them, as I have explained 

 above. I therefore suggest reserving for these individuals the name of 0. meridion- 

 alis, a denomination which has undoubtedly been applied by Lyman to a certain 

 number of similar specimens. In order to clear up any confusion, I think I had 

 better give of that species a somewhat detailed description, and two photographs 

 which reproduce respectively the dorsal and the ventral faces. 



The disk is rounded, not at all excavated in the interradial spaces; it is rather 

 thick and the upper face is more or less bulging. But this face is completely covered 

 by small, very dense, elongated and fairly thin spines which display on their surfaces 

 a few more or less developed asperities or irregular denticulations, and are terminated 

 by a few rather scarce and unequal spinules which amount to two or three only. 

 These little spines completely hide the outlines of the adjacent plates. Sometimes 

 there are seen radial ribs which are little protruding, but the radial shields them- 

 selves are partly covered by stumps and their distal part alone is visible; they are 

 widely separated. 



On the under face of the disk, the small spines become less and less important, 

 as they come nearer to the mouth shields, and they are finally reduced to the state of 

 mere conical, rough granules; the underlying plates then become apparent; they are 

 very small, rounded, and more or less imbricated. The genital slits are elongated 

 and broad. 



The mouth shields, which are of middle size, have a shape analogous to that of 

 0. pentacrinus, that is to say, they are triangular, much wider than long, with an 

 obtuse proximal angle limited by two straight sides, rounded lateral angles and a 

 convex distal side which often shows in its middle a little lobe, which, by the way, 

 is very variable in size. The adoral plates are elongated, fairly narrow, with 

 parallel sides which are almost straight; they are from three to three and a half 

 tunes longer than wide, inwardly contiguous, and they outwardly build, although 

 without growing wider, a more or less conspicuous blade which separates the mouth 

 shield from the first lateral brachial plate. The oral plates are fairly high and 

 triangular. The oral papillae number three on each side; the external one is 

 widened, flattened, and squamiform, without, however, offering an excessive 

 development, and the other two are conical and pointed. The dental papilla, 

 which is single, is strong and conical. 



The arms are moniliform, less so, however, than in 0. pentacrinus. The shape 

 of the upper brachial plates very much recalls that observed in this latter species; 



