OPHIURANS OF UNITED STATES NATIONAL MUSEUM. 99 



OPHIACANTHA (OPHIOTRETA) AFFINIS, new species. 

 Plate 13, figs. 1-3. 



Albatross station 2156. Apr. 30, 1884. Lat, 23 10' 35" N.; long. 82 21' 

 55" W.; 278 fathoms; co.; temp. 59.8 F. One specimen (type). 



Albatross station 2321. Jan. 17, 1885. Lat. 23 10' 54" N.; long. 82 18' W.; 

 230 fathoms; fne. gy. s. Two specimens. 



Albatross station 2346. Jan. 20, 1885. Lat. 23 10' 39" N.; long. 82 20' 

 21" W.; 200 fathoms; co. One specimen. 



Albatross station 2348. Jan. 20, 1885. Lat. 23 10' 39" N.; long. 82 20' 

 21" W.; 211 fathoms; co. One specimen. 



Type. Cat. No. 7178, U.S.N.M. 



The diameter of the disk ranges from 14 to 16 mm., and in one of the specimens 

 from station 2321, it does not exceed 11 or 12 mm. The arms are seldom complete 

 and they are broken at a certain distance from the base, but they are long, and, in 

 the smallest example from station 2321, one arm, which remains complete, measures 

 1 10 mm. Besides, the specimens are generally not in very good condition and they 

 have undergone some friction which has often taken away part of the spines of the 

 upper face of the disk; this face itself is sometimes torn. 



This species is very interesting because it recalls, by several characters, Ophio- 

 pristis ensifera of Verrill, while by some others it is near Ophiaeantha (Ophiotreta) 

 valenciennesi. I shall describe it chiefly from the sample from station 2156, the 

 diameter of the disk of which reaches 15 mm., and two arms of which are preserved 

 to a certain length (70 and 55 mm., respectively). 



The disk is rounded or subpentagonal. The upper face, slightly convex, is 

 covered with small, thin, imbricated plates, the outlines of which are well per- 

 ceived only when the spines borne by them are removed. Each of them is 

 provided with a short and conical spine, which is very thick at its base, so as to 

 beset a large part of the surface of the plate, two or two-and-a-half times longer 

 than wide and provided on its surface with fairly strong asperities which often 

 become a little more conspicuous at the end of the spine, where there are always two 

 or three of them. These spines always leave bare the radial shields, the outlines 

 of which are quite apparent; the latter are small, oval, or triangular, with rounded 

 angles, one-and-a-half times longer than wide, and widely separated by several 

 rows of plates, the middle one of which often includes two or three plates which 

 are larger than the others. 



The under face of the disk is covered in the interradial spaces with plates 

 identical with those of the upper face, but deprived of spines, and extending as 

 far as the mouth shields. The genital slits are long and narrow. 



The mouth shields are large and widened and recall those of Ophiopristis 

 ensifera of Verrill; they are triangular with a fairly open proximal angle which is 

 limited by straight or slightly incurved sides; the lateral angles are very wide and 

 strongly rounded; finally the distal side offers in its middle a wide lobe which does 

 not very strongly protrude into the interradial space; these shields are one-and-a- 

 half times wider than long. The adoral plates are narrow and greatly elongated, 

 inwardly widened, and they rest against each other, following the interradial 

 median line, for a fairly important length; they become narrower in their middle 



