40 DR. R. V. WILLEMOES-SUHM ON SOME ATLANTIC 



funiculus and two flagella ; scale of the second antennae jointed; upper lip triangular ; 

 rnandibulse with a three-jointed palpus ; no deep excision in the under lip. Second 

 process of the first maxilla without denticulation ; second maxilla with an elongated 

 flagellum and a small palpus ; maxillipedes terminated by a denticulated claw, with large 

 palpus and flagellum. Gnathopoda and first pereiopod used as maxillipedes, shortened 

 and recurved ; second, third, and fourth pereiopod having nearly the length of the body, 

 terminated by a long denticulated claw ; last pair of pereiopods shorter, terminated by a 

 rounded joint, very hairy, and without branchiae. Three branches of branchiae on the 

 base of the gnathopoda and first four pereiopoda, two of which are covered by the cara- 

 pace. Breeding-lamellaB on all the gnathopoda and pereiopoda. No pseudo-segmentation 

 on the sixth segment of the pleon. External caudal appendages jointed. 



Chalabaspis unguicttlata, n. sp. , 



Length 35-37 millims. 



Mode of Life, and Colour. 



We have already seen at the beginning of this description that this is the commonest 

 deep-sea Schizopod with as wide a geographical as bathymetrical distribution. It lives 

 together with the same fauna as Gnathophausia zoea, which several times came up 

 accompanied by Chalaraspis. Its colour is a bright red. 



3. On Petalophthalmus, a Mysidiform Schizopod. (Plate VII.) 

 In Prof. Wyville Thomson's ' Depths of the Sea,' p. 176, there is a quotation from a 

 preliminary note of the Rev. A. Merle-Norman, according to which specimens of Ethusa 

 granulata, a brachyurous Decapod, taken in 110-370 fathoms, are apparently blind, but 

 have two remarkable spiny eye-stalks, with a smooth rounded termination, where the eye 

 itself is ordinarily situated. In other specimens of the same crab the rostrum disappears 

 entirely, and the two eye-stalks, approaching each other, assume its functions. In 

 accordance with the altered conditions of life, the eyes and their stalks seem to undergo 

 in Ef'ethusa the most extraordinary modifications. 



The same thing which now-a-days happens to a crab living in different conditions of 

 life has evidently also happened (but in the course of ages probably) to a Schizopod, in 

 which we find at the top of the eye-stalks, instead of organs of vision, two flat spherical 

 terminations in which no trace of an eye (which one would expect to find in this place) 

 has been left. But this peculiarity in the Schizopod seems not to be a modification of 

 individuals exposed to certain conditions of life ; for we got specimens from very different 

 depths (1590-2500 fathoms) and latitudes, from the mid- Atlantic near St. Paul's Pocks 

 down to the southern regions of Tristan d'Acunha, in both sexes of which the conforma- 

 tion of the eye is exactly the same. Though in the whole these Schizopods approach the 

 genus Mysis, we shall find that they have several peculiarities which do not allow us to 

 suppose that this is a Mysis which, like the above-mentioned Ef ethusa, has changed 

 when exposed to certain conditions of life, and of which specimens might exist now- 

 a-days in full possession of their organs of vision. Once, of course, this process must 

 have taken place, but probably at a time when such Schizopods as Gnathophausia and 



