42.2 
CRUSTACEA. 
/ 
British species, having the frontal rostrum not extending beyond the peduncle of the superior antenna:, and 
nearly straight. j 
[Other genera have been proposed by Risso, Leach, P. Roux, and M. Edwards, founded upon variations in the I 
form and proportions of the legs.] 
Pasiphcea, Savigny, is a very interesting genus, allied to the preceding in the upper antennae, terminated by j 
two filaments ; the four fore-legs terminated by a didactyle claw, but [differing from all the other Carides] in 
having the external base of the legs furnished with a thread-like appendage ; the claw-legs ai’e larger, nearly equal 
in size, very slender, and filiform ; the body is very long, very compressed, and very soft. Type, P. Sivado, Risso. 
Found in the Mediterranean, especially in the Bay of Nice, where it is very abundant.* 
The fifth and last section of the Macroura — that of the Schizopoda — appears to unite them with j 
the subsequent order. The legs are very slender, like flattened threads, and not furnished with claws, 
but having a longer or shorter lateral appendage arising on their outside near the base, and [the legs 
are] fitted only for swimming. The eggs are borne between them, and not under the tail. The ocular 
peduncles are very short. As in the majority of the Macroura, the front is prolonged into a kind of 
rostrum. The carapax is very slender. The tail terminated, as is customary, in a swimmeret. These 
Crustacea are minute and marine. 
In some, the eyes are very apparent ; the lateral antennae furnished with a scale ; the intermediate 
ones terminated by two filaments, and composed of many minute joints, as in the preceding.f 
Mysis, lja.tr., has the antemise and legs uncovered; the carapax long, nearly square, or cylindrical ; the eyes 
close together ; and the legs capillary, and formed of two thread-like fila- 
ments. Type, M. Fabricii, Leach ; Cancer scutatus, O. Fabricius. 
[The species of Mysis are termed Opossum Shrimps, from their singular 
economy of carrying their eggs and young in a large pouch, with membranous 
envelopes, beneath the thorax and between the thoracic legs. Their structure 
has been fully investigated by Thompson in his Zoological Researches. In 
the Encyclopedie Methodique are also some figures communicated by Dr. 
Leach to Latreille, and evidently intended for the Malacostraca Britannica 
of the former author, but which were never published by him. 
Two other genera, nearly allied to Mysis, have been proposed by Thompson, 
founded upon oceanic species, namely : — 
Cynthia, having branchiae attached to the subabdominal fins ; and Noctiluca, j 
founded upon a luminous species, but not described with sufficient precision, | 
and omitted by M. Edwards. 
Thysanopoda (Edwards), in which there are also eight pairs of bifid natatory feet, but the branchiae are in the 
form of many-branched, membranous appendages, at the base of the true legs. 
The genera Phasmatocarciniis, Tilesius (in the Neue Annalen Wetterausch Gesellschaft, vol. i.), considered by 
Thompson and Edwards as undescribed, and named by the former Lucifer {Leucifer, Edwards), and that of Podop- j 
sis by Thompson, are amongst the most singular of known Crustacea, having a filiform body, with very large 
globular eyes placed at the extremity of very long and laterally extended foot-stalks ; and the legs are exceedingly 
slender and short. According to Slabber, whose figure of one of the species has been overlooked by all Crustace- 
ologists, there are eight pairs of legs of equal size.] 
Cryptopus, Latr., has the carapax subovoid, swollen, bent under at the sides, enveloping the body, as well | 
as the antennae and legs, having only on the under side a longitudinal slit. The eyes are wide apart. The : 
legs are like flattened threads, with a lateral appendage. Type, C. Defrancii, Latr. Mediterranean. 
In others, the eyes are hidden. The intermediate anteanae conical, exarticulated, and very short. The lateral 
antennae composed of a peduncle and a filament, without distinct articulations : their base is not protected by a 
porrected scale. 
Mulcio, Latr., has the body very soft ; thorax ovoid ; legs like flattened threads, the majority with an ap- 
sophical Traiisuct'wns, that it is a Decapod ; and therefore the observa 
tinns of Latreille, at the end of the Decapods, cannot be adopteu.] | 
t [The Schizopoda having, since the publication of the second edi- 
tion of tiiis work, been well investigated by Edwards and Thompson, 
have been found to be more nearly allied to the order Stomapoda, 
although presenting so near a resemblance to the Carides. This inno- 
vation was adopted by Latreille himself in his Cours d’Entonwlosic, 
in which this author has proposed to give tliose Podopthalmous 
Crustacea wiiich are destitute of thoracic interna! branchise, but 
otherwise resembling the Carides, the sectional name of Caridioides, 
indicative of their analogy with the last-named group. The typical 
genus Mysis is especially interesting, on account of the complete 
transformation of all the three pairs of foot-jaws into legs, so that, to- 
gether with the five pairs of true legs, there are eight pairs of loco 
motive organs ; and as each of these is divided from the base by the 
addition of a lateral appendage, these animals may be said to have not 
fewer than thirty-two legs.) 
* [Many additional genera have been added to the Carides by Poly- 
dore Roux in his Mhnoire sur la Classijtsation des Crustacis de la 
Tribu des Salicoques, Marseilles, 1831 ; and by Milne Edwards in the 
jinnales des Sciences Naturelles, and Hist. Nat. des Crustacis. Of 
these it will be necessary only to notice those of Sicyonia, nearly 
allied to PeniEus, but differing from it and alt the other genera in 
having no appendages to the false subabdominal legs, and in the modi- 
fications of its respiratory apparatus, there being only eleven pairs of 
branchiae instead of eighteen. Sergestes and Acetes — in which the 
posterior pair of true legs is almost rudimental, or entirely obsolete, 
the outer pair of foot jaws being immensely developed, so as to consti- 
tute an anterior pair of legs to supply their place. These genera are 
founded upon exotic species.] 
[Here terminates, in the system of M. Edwards, the great order of 
Decapod Crustacea, which, in his Hist. Nat. des Crustaces, is suc- 
ceeded by an appendix consisting of “ Decapodes douteux,” compris- 
ing the genera Zoea, Cerataspis, Mulcio, and Posydon. With respect 
to Zoea, I liave clearly proved in my Memoir, published in the P/iilu- 
Fig. 8. — Mysis vulgaris, about twice the 
natural length. 
a, one of the bifid legs. 
