178 THE VOYAGE OF H.M.S. CHALLENGER. 



off Greenland, and also occurring along the coasts of Norway, where two other species, 

 Boreomysis tridens, G. 0. Sars, and Boreomysis megalops, G. 0. Sars, have been also 

 observed. Moreover, on the Norwegian North Atlantic Expedition two large species 

 were taken, Boreomysis nohilis, G. 0. Sars, and Boreomysis scyphops, G. 0. Sars, the 

 latter of which is also represented in the Challenger collection. Finally, there are two 

 additional species from the Challenger Expedition, to be described further on. The total 

 number of species thus amounts to seven. All are true deep-sea forms, the animals 

 descending to very considerable depths, and having never been met with in shallow 

 water. 



The following is a synopsis of the three Challenger species : — 



imperfectly developed, calyciform, without pigment or visual elements, . B. scyphops, G. 0. Sars. 



Eyes 



of the usual 

 structure, 



short and thick, almost circular, with cornea greatly expanded. 



Frontal margin obtusely rounded, . . . B. ohtusata, G. 0. Sars. 



narrow, almost fusiform, with cornea very small. Frontal 



margin with a small pointed projection in the middle, . B. microps, G. O. Sars. 



43. Boreomysis scyphops, G. 0. Sars (PL XXXII. figs. 10-20). 



PetalojMhalmus inermis, Suhm MS. 



Boreomysis scyphops, G. O. Sars, Crustacea et Pycnogonida nova in itinere 2do et 3tio 



Expeditionis Norvegicse anno 1877-78 collecta, No. 3. 

 Boreomysis scyphops, G. O. Sars, The Norwegian North Atlantic Expedition, 1876-1878, 



Crustacea, i. p. 56, pi. vi. 



Specific Characters. — Frontal part of carapace without any distinct rostrum, 

 projecting but slightly in the middle ; antero -lateral lobes obtuse at apex. Eyes without 

 pigment or visual elements, constituting two pedunculated concave, or well-nigh calyciform 

 lamellae, placed vertically. Antennular peduncle comparatively smaller than in the other 

 species, and of more noi-mal form. Antennal scale rather elongate, about twice as long 

 as antennular peduncle, slightly tapering, denticle of outer corner somewhat projecting. 

 Propodal joint of legs subdivided into two articulations only ; exopods remarkably 

 elongate, with terminal part composed of numerous articulations. Telson almost 

 equalling in length the two preceding segments taken together, outer part slightly 

 tapering, and fringed with numerous small denticles, apical incision narrow, occupying 

 nearly one-fourth of the length of telson. Inner plate of urojioda reaching tip of telson, 

 outer plate much larger. " Colour a uniform pale red. Length reaching 85 mm. 



Remarhs. — This gigantic Mysidan was first met with on the Challenger Expedition 

 in the subantarctic region of the Southern Ocean, and has been briefly recorded by the 

 late Dr. v. Willemoes-Suhm under the provisional name of Petalophthalmus inermis. 

 Subsequently the same form was obtained on the Norwegian North Atlantic Expedition 



