OPHIUBANS OF UNITED STATES NATIONAL MUSEUM. 107 



OPHIOMITRELLA PORRECTA, new species. 



Plate 12, figs. 5-6. 



Albatross station 2781. Feb. 4, 1888. Lat. 51 52' S.; long. 73 41' W.; 369 

 fathoms; bu. m.; temp. 49.9 F. Three specimens. 

 Type. Cat. No. 32299, U.S.N.M. 



The diameter of the disks measure, respectively, 6.5, 4.5, and 3 mm. ; in the 

 largest specimen the length of the arms reaches 28 mm. 



The disk is rounded and subpentagonal but not excavated in the interradial 

 spaces. The upper face is covered with fairly large imbricated plates, the outlines 

 of which are not very conspicuous in the largest specimen, owing to their being hidden 

 by the tegument, but these outlines are more distinct on the two smaller specimens. 

 On the latter, also, it is more easy to discern the presence of small elongated radial 

 shields, which are triangular and narrow, widely separated, while they are hardly 

 distinct from the neighboring plates on the largest specimen. Each plate carries 

 a large spine which is very rough, rather short, thick at its base, and has about the 

 same width over its whole length. At the end of the said spine appear a few large 

 unequal, and irregularly arranged spinules, which may in turn carry some secondary 

 denticulations; it happens often, but not constantly, that the spinules amount to 

 three and are arranged divergently. The length of the spines is variable. Instead 

 of being cylindrical, the spines may be simply conical, and, in this case, they are 

 provided only with strong rugosities. 



The under face of the disk is covered with rounded and imbricated plates, the 

 outlines of which are more distinct than on the upper face, and each of which carries 

 a conical spine which extends as far as the mouth shield. These spines are always 

 very rough, but the terminal crown of spinules has disappeared. The genital slits 

 are wide. 



The rather small mouth shields are lozenge-shaped with an obtuse proximal 

 angle, a very much rounded distal angle, almost equal and straight sides; they are 

 somewhat wider than long. The rather small adoral plates are fairly wide, but 

 short, twice or two and a half times longer than wide; they are widened outwardly, 

 but they do not separate the mouth shield from the first lateral brachial plate. 

 The oral plates are narrow and elongated. The oral papillae amount to three on 

 each side; they are elongated, conical, and rough, fairly strong; the external oral 

 papilla has about the same shape as the other two, although its end is a little more 

 obtuse. The single tooth papilla is a little stronger but of the same shape as the 

 neighboring ones. 



The middle-sized upper brachial plates are triangular, with a fairly open 

 proximal angle and a convex distal side; they are about as wide as long, or a little 

 wider than long, and widely separated from the basis of the arms. 



The first under brachial plate is fairly large, pentagonal, with a narrow proxi- 

 mal side, two diverging lateral sides excavated by the tentacular mouth pore, and 

 two distal sides which meet by a very obtuse angle. The succeeding plates are 

 pentagonal, with an obtuse proximal angle, lateral sides which are slightly excavated 

 by the tentacular scale, and a wide and convex distal side. These plates are at 

 first a little wider than long, then they finally become a little longer than wide; 



