OPniUEANS OF UNITED STATES NATIONAL MUSEUM. 103 



Albatross station 2415. Apr. 1, 1885. Lat. 20° 44" N.; long. 79° 26' W.; 

 440 fathoms; co. crs. s. sh. for.; temp. 45.6° F. Fifteen specimens. 



Albatross station 2663. May 4, 1886. Lat. 21° 56' X.; long. 79° 49' W.; 421 

 fathoms; br. s.; temp. 42.7° F. One specimen. 



Havana. One specimen. 



The shape of the mouth shields varies somewhat, the proximal angle being 

 more or less elongated and pointed, but they are always longer than wide. The 

 granules of the upper face of the disk extend generally over to the first one or two 

 upper brachial plates, and, on certain specimens, especially on some from station 

 2415, one may observe on the plates at the bases of the arms, from two to four very 

 short spines which start from the middle of the distal side. 



I have already called attention to the wide geographical range of 0. valeiv- 

 ciennesi (06, p. 293, and 09, p. 189). The discovery of this species at station 2334 

 is very interesting since it shows that it can come up as liigh as 67 fathoms. I have 

 examined mth special attention the specimen from that station; though rather 

 small, the diameter of the disk not exceeding 7 mm., it is quite characteristic and 

 there can be no doubt as to its identity. 



OPmOMITRELLA AMERICANA, new species. 

 Plate 15, figs. 1-2. 



A single example found on a branch of Platycaulis danielsseni. 



Type.— Cat. No. 32297, U.S.N.M. 



The diameter of the disk reaches 6.5 mm. The arms are not complete; they 

 are preserved to a length of 12 to 15 mm. and could not have been very long. 



The disk is subpentagonal. The upper face is covered with fairly thick and 

 sharply outUned plates, rather large, somewhat unequal, polygonal, with more or 

 less rounded angles and not imbricated. These plates bear large tliick globules 

 which are a Uttle higher than wide and cyUndrical with rounded ends and carry 

 very short, fine, and pointed spinulcs. The smaller plates bear but one globule 

 each but most of them have two and few have even three; nevertheless these glob- 

 ules always remain broadly separated from each other and are relatively few; 

 they lie closer to one another only at the margin of the disk. The radial shields, 

 of medium size, are larger than the largest plates of the disk, triangular, with a 

 plainly rounded proximal apex; they are as long as wide or a little longer than 

 wide; their surface is completely bare, but on their external edge are found a certain 

 number of granules, amounting to about half a dozen, identical with those existing 

 on the margin of the disk. These sliields are wide apart and the intervals between 

 them are beset by plates wliich are usually arranged in one row only and may reach- 

 a large size. The under face of the disk is covered all over with plates similar to 

 those of the upper face, but smaller, somewhat lubricated, and carrying granules 

 which, on the margin, are identical with those of the upper face which they succeed; 

 these granules become smaller and less rough as they he nearer the mouth shields. 

 The genital slits are very wide. 



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

 elongated proximal angle which has a rounded apex; the two lateral sides, slightly 

 excavated, meet the strongly convex distal edge by rounded angles; in the middle 

 6061°— Bull. 84—14 8 



