ISOPODA OF THE 'LIGHTNING-' AND OTHER EXPEDITIONS. 99 



to the outer margin ; the nail of the finger closes down into the cavity within the 

 thumb-nail and on the truncated end of the thumb. 



The second gnathopods (n. cjn-) resemble those of Sphyrapus tudes, but the basos is 

 narrower, being only slightly broader than the following joints; the meros has one 

 distal spine on the front margin, the wrist a row of five spines, and the hand the same 

 number ; the finger is much curved, slender, and its margin smooth. 



In the first peraeopods (u.prp 1 ) the wrist is a little dilated, the hand flat, long, 

 curved, with seven slight spines on the front margin, and much ciliated on both 

 margins. 



The second peraeopods (n.prp 2 ) are shorter than any except the last; the third 

 (ir. prp % ) have the hand short, distally dilated, and then surrounded by a fence of 

 biserrate spines of varying lengths. The fourth and fifth (n. prp*) pairs are similar in 

 form, but the fifth is smaller than the fourth ; the wrist is longer than the hand, which 

 is small, ciliated, and having two long spines near the base of the finger. 



The uropods (in. d $ ) have the peduncle as long as the segment minus its produced 

 apex, and a little dilated distally ; the inner branch is long, with about 15 articulations, 

 which vary irregularly in length ; the outer branch is very slight, and composed of 

 3 articulations. Judging from the spirit-preserved specimens the uropods in this 

 species would seem to be carried divergently, not following behind parallel to each 

 other. 



Sphyrapus malleolus may at once be distinguished from its allies, not only by the 

 form of the gnathopods, but by the rudimentary condition of the inner flagellum of the 

 upper antenna?, which is reduced to an unjointed minute tubercle, and by the spine- 

 formed wings of the second segment of the pleon. 



The species has been procured in the abyss of the North Atlantic in four 

 dredgings : — 



1. 'Porcupine,' 1869, Station 22, lat. 56° 8' K, long. 13° 34' W., 1263 fathoms. 



2. 'Porcupine,' 1869, Station 24, lat. 56° 26' N., long. 14° 28' W., 109 fathoms. 



3. 'Porcupine,' 1870, Station 17a, lat. 39° 39' N., long. 9° 39' W., 740 fathoms. 



4. 'Valorous,' 1875. Station 11, lat. 57° 11' N., long. 37° 41' W., 1450 fathoms. 

 The first two of these localities are to the south of Rockall, and may be considered to 



be within the bounds of British seas ; the third is to the west of Portugal ; the last lies 

 directly south of the southernmost point, Cape Farewell, of Greenland. 



2. Sphyrapus tudes, n. sp. (Plate XXII. fig. i.) 



The carapace (i. d) has a short triangular rostrum, from which it slopes gently back- 

 wards to the insertion of the small bulbous, apicate, ophthalmic processes. Behind these 

 the lateral margins are slightly convex ; the two perseon-segments, which are coalesced 

 with the head, are successively wider ; the coxal portion of the first has a large ventral 

 fold. Behind the cephalic region the animal gradually tapers to the last pleon-seg- 



