268 A IIISTORY OF RECENT CRUSTACEA 
unabashed author himself remarks that ‘this genus was 
instituted by Mr. Leach, who has derived the name from 
the English word prawn. He assigned to it the species 
flexuosus, Miiller, and integer, Leach. 
Petalophthalmus was so called from having the eyes 
leaf-like. They are described in the single species, Petal- 
ophthalmus armiger, as ‘quite rudimentary, without any 
trace either of pigment or visual elements, constituting 
merely two thin and pellucid lamelle, of an oblong form, 
and mounted on very short and narrow pedicles.’ ‘The 
species was obtained in the tropical Atlantic from a depth 
of 2,500 fathoms. The telson is not incised at the apex. 
The male is distinguished by the astonishing and perhaps 
unique development of the mandibular ‘ palp,’ and by the 
lamellar prolongation of the fourth joint in the first and 
second maxillipeds, the first pair being, contrary to the 
custom in this family, devoid of exopod and epipod. A 
female with seven pairs of marsupial plates has been, per- 
haps incorrectly, assigned to this species. 
For the preoccupied Arctomysis, Hausen, I propose the 
name Hansenomysis. It has a short carapace, the mandi- 
bles with prominent cutting edge, long molar tubercle, 
and very large ‘palp, the first maxillipeds withont 
exopod, and with none of the joints expanded, but with an 
epipod, the second maxillipeds with a small ovigerous plate 
at the base, and the short fourth joint expanded into a 
large plate. The three following pairs of appendages are 
very slender, with a short hairy terminal joint, and there 
is a very long, sharp, bare nail on the next three pairs. 
Hansen considers that his Hansenomysis Fylle and the 
male of v. Willemoes Suhm’s Petalophthalmus armiger 
might form a separate family inthe Schizopoda. The sup- 
posed female of the latter species he regards as belonging 
to Boreomysis scyphops and not to Petalophthalmus. 
Boreomysis, of which the type species is Boreomysis 
arctica (Kroyer), taken off the coasts of Greenland and 
Norway, includes among others Boreonvysis scyphops, Sars, 
which is far from being only a boreal Mysis. It was in 
fact first met with by the Challenger at great depths in the 
