REPORT ON THE SCHIZOPODA. 179 



in the Arctic Sea, and has been more fully described by the author under the name of 

 Boreomysis scyphops. Although the former appellation has without a doubt claim to 

 priority, I have seen fit to retain that proposed by myself, for the following reasons : — 

 First, it is obvious that the said form cannot properly be comprised within the same 

 genus as the preceding anomalous Mysidan, the only characters peculiar to both being 

 merely the rudimentaiy condition of the eyes, whereas in all other respects it agrees much 

 more closely with the species of the genus Boreomysis, to which of course it should 

 rightly be referred. Secondly, this admitted, the specific name inermis would be quite 

 inappropriate, referring, as it does, to the absence in the male of similar prehensile organs 

 as in Petalophthahnus armiger, such a peculiar prehensile apparatus being never found 

 in any species of the genus Boreomysis. Thirdly, no description of this form has been 

 given by the late Dr. v. Willemoes-Suhm, by whom the animal is only briefly recorded 

 as a new species. 



Although a full account of the present interesting Mysidan, with figures representing 

 both sexes, has been given in the ReiJort on the Crustacea collected on the Norwegian 

 North Atlantic Expedition just published, I have deemed it advisable to append the 

 following somewhat modified description of the Challenger form. 



Description. — Most of the specimens in the collection are females, and of the two nlale 

 specimens found, none is yet fully developed. The largest female specimen measures about 

 85 mm. in length from the tip of the antennal scale to that of the uropod, or still 

 somewhat more than the arctic specimens collected on the Norwegian Expedition. 



The form of the body (see PI. XXXII. fig. 10) is somewhat robust, with the anterior 

 and posterior divisions pretty well defined. 



The carapace is rather large, covering the whole of the trunk, except a small part of 

 the last segment, which appears exposed above. Moreover, the rounded lateral parts or 

 wings of the carapace slightly overlap the first caudal segment. The cervical sulcus is 

 very distinctly defined, marking off" the cephalic Section or frontal part of the carapace. 

 The latter portion is evenly arched above, without any keel, and juts forth anteriorly in 

 the middle as a slightly projecting angle. At the sides, the frontal margin forms, as in 

 the other species, a deep emargination almost wholly exposing the basal part of the 

 antennae (see figs. 10, 11). Beneath this emargination each of the antero-lateral corners 

 projects as a linguiform lobe, obtuse at the tip. The dorsal area is seen extending 

 posteriorly behind the cervical sulcus as a narrow linguiform space, reaching to about the 

 posterior third of the length of the carapace. 



On removing the free parts of the carapace (see fig. 11) all the segments of the trunk 

 are visible, as in the Lophogastridaj and Eucopiidse, distinctly defined in their whole 

 circumference, though densely crowded dorsally, in such a manner that only the last 

 segment has the dorsal face of any considerable extent, whereas the others are extremely 

 narrow, almost riband-shaped in that part. Laterally, each of the six anterior segments 



