112 BULLETIN 84, UNITED STATES NATIONAL MUSEUM. 



the Resultats ties campagnes scientifiques du Prince de Monaco, but the rather 

 important pamphlet in which my paper is included did not come out untU 1909; 



1 was also unable to insert in it the synonymy wliich I am estabhshing here. 



Having now explained this situation I beg to recall that 0. minima was 

 found by the expeditions of the TravaiUeur and of the Talisman, about latitude 

 41°_44°']Sr., and longitude 9°-ll° W., between 1,220 and 1,350 m., and by the 

 Princesse Alice in latitude 32° N., and longitude 16° W., at 1,425 m. 



This species is always very small, the diameter of the disk scarcely exceeding 



2 to 2.5 mm.; the specimen from station 7283 is somewhat stronger than the others. 



OPmOTREMA GRACILIS, new species. 

 Plate 12, figs. 1-2. 



Albatross station 2751. Nov. 28, 1887. Lat. 16° 54' N.; long. 63° 12' W.; 

 687 fathoms; bu. glob, oz.; temp. 40° F. One specimen. 

 TVpe.— Cat. No. 32301, U.S.N .M. 



The sample is not perfect for the under face of the disk is partly torn away; 

 the other parts are fairly well preserved. Ahnost all the arms are complete; they 

 are slender and about 45 to 50 mm. long. The disk is somewhat disfigured and 

 stretched along two radii, therefore one of the diameters equals 11 mm. while 

 the other is only 8 mm.; its outHne is pentagonal but the sides are unequal owing 

 to the deformity sustained; moreover, some of the sides are straight or shghtly 

 excavated, and the others are a httle convex. 



The upper face of the disk is depressed and covered with small fine plates 

 which are equal, hardly imbricated and almost rounded with very sharp outhnes. 

 Each of these plates carries at its middle a small slender spine, which is conical, 

 rather short, with an elongated and sharp point. The radial shields, although 

 rather small, are quite distinct from the neighboring plates; they are elongated, 

 triangular, twice longer than wide with a rounded distal margin and a very acute 

 proximal angle; their surfaces are absolutely bare. The two shields of each pair 

 are arranged more or less divergently but they are always separated from each 

 other by several series of plates. 



The under face of the disk is covered all over by plates identical with those of 

 the upper face, but the spines borne by the former do not appear except in the 

 distal half of the disk and do not reach the mouth shields. The genital sHts are 

 narrow but plainly visible. 



The mouth shields are middle-sized, triangular, much wider than long, with a 

 widely opened proximal angle, and almost straight lateral sides joining by rounded 

 angles the distal side which displays in its middle a rounded lobe rather strongly 

 protruding in the interradial space. The adoral plates are extremely elongated and 

 much thinner on all the part which is close to the mouth shield, but on the contrary 

 broadly widened outwardly where they constantly form an important lobe which 

 widely separates the mouth shield from the first lateral brachial plate; they are 

 inwardly contiguous on the interradial median line, where their ends become rounded 

 and sometimes also sUghtly widened. The oral plates are high and narrow. On 



