REPOET ON THE BRACHYURA. 
331 
The larger male differs not only in the small subequal chelipedes, but also in the 
form of the post-abdomen, which is slightly broader in proportion to its length. 
Ethusina, Smith. 
Ethusina, Smith, Ann. Rep. Com. of Eish and Fisheries, 1882, p. 349, 1884. 
This genus (or subgenus as I prefer to regard it) is, according to Smith, closely allied 
to Ethusa, but is distinguished by the form of the antennules, whose basal segments are 
very large and swollen, occupy the whole width of the front, and crowd back the eyes 
and antennae into an almost transverse position, nearly beneath the exterior orbital 
angles, which are reduced to small lateral teeth, far back from the front. The eye-stalks 
are very small and immovably imbedded in the orbits, which closely inclose them to near 
the tips, except for a narrow space beneath. 
In the typical species Ethusina abyssicola, Smith, dredged off the east coast of the 
United States (1497 to 1735 fathoms), there are, according to Professor Smith, no podo- 
branchiae at the bases of the first gnathopods, so that there are only six branchiae on each 
side ; two arthrobranchise each at the base of the second gnathopod and first pereiopod, 
and one pleurobranchia each for the second and third pereiopods. 
There are in the collection of H.M.S. Challenger two species, which on account of the 
structure of the antennules and eye-peduncles I assign to this genus. One of these 
species is unfortunately represented only by a single mutilated example. 
Ethusa {Ethusina) challengeri, n. sp. (PI. XXYI1I. fig. 2). 
Carapace about as broad as long, depressed above, with the cervical and cardiaco- 
branchial sutures very indistinctly defined ; the lateral margins nearly straight, and 
converging to the front, so that the body, as in Ethusina abyssicola, is much narrower in 
front than posteriorly. The front is not quadridentated, but sinuated, and concave in 
the middle line, where it is prolonged downwards (as in Ethusina abyssicola) between the 
bases of the antennules, and is in contact with the narrow median process of the epistoma. 
The orbits are very incompletely defined, and the exterior orbital spine or tooth, which is 
developed on one side only, is very short. The post-abdomen (in the female) is dis- 
tinctly seven-jointed. The eye-peduncles are short, and taper from the bases to the 
distal extremity ; the eyes are small, and terminal. The bases of the autennules are very 
large and swollen, subglobose. The basal joint of the antennae is short and slender, and 
does not nearly attain the front (the flagellum is broken in the specimen examined). 
The exterior maxillipedes do not cover the anterior part of the buccal cavity, which is 
narrowed very abruptly (as in Ethusina abyssicola) ; the ischium is produced and 
rounded at its antero-internal angle. The merus is distally somewhat rounded, and is 
