194 
CRUSTACEA. 
which are strongly sulcated witli longitudinal ridges. The right 
one is the largest *. 
A fourth from the same sea is removed from the preceding by 
several characters, and merits the distinction of forming a separate 
subgenus, the Prophylax, Latr. The tail, with the exception of the 
superior surface of the three last segments, instead of being soft 
and arcuated, and having but a single range of oviferous filaments, is 
covered with a coriaceous tegument, is straight, and is only curved 
beneath at its extremity ; its inferior surface presents a groove and 
two rows of false feet. The body also is linear, and the two lateral 
appendages of the end of the tail are almost equal, the larger divi- 
sion being foliaceous and ciliated. The last four feet are slightly 
graniilated at their extremity, and appear to be terminated by a sin- 
gle finger, or at least are not distinctly bifid. Perhaps we should 
refer to this division those Paguri whicli inhabit the Serpulse, and 
Alcyonii, such as the Pagurus tubularim, Fab. 
In all the following Macroura, the two posterior feet at most are 
smaller tlian the preceding ones. Most generally the sub-caudal 
false feet form five pairs. The teguments arc always crustaceous. 
The lateral fins of the penultimate segment of the tail, and its last, 
form a common one arranged like a fan. 
The two subsequent sections possess a common character, which 
separates them from the fourth or that of the Carides. The antennee 
are inserted at the same height, or on a level; the peduncle of the 
lateral ones, Avhen accompanied by a scale, is never entirely covered 
bv it. There are frequently Imt four pairs of sub-caudal false feet. 
The two mediate antemicfi are always terminated by tAVO filaments 
only, usually shorter than their peduncle, or scarcely any longer. 
The external leaflet of the natatory appendages of the penultimate 
segment of the tail is neA'or divided by transverse suture. 
In our second section, or the Locusts, so called from the name 
Locusta giAmn by the Latins to the most remarkable Crustacea, of 
this division, and fromAvhich is derh^ed that of Langousle, applied to 
them in France, there are never more than four pairs of false feet. 
I'he posterior extremity of the fin that terminates the tail is ahvays 
nearly membranous, or less solid than the rest. The peduncle of 
the mediate antennae is ahvays longer than the tAVO terminal filameiits, 
and more or less bent or geniculate ; the lateral ones are neAmr fur- 
nished Avith scales ; sometimes they are reduced to a single peduncle 
Avhich is dilated, \mry flat, and in the form of a crest ; sometimes they 
are large and long, terminating in a point and bristled Avith spines. 
All the feet are nearly similar and end in a point ; the tAA’o first are 
merely somcAvhat larger ; their penultimate joint and that of the tAvo 
last are at most unidentated, but Avithout forming Avith the last a per- 
* For the other species see the article Pmjure, Encyc. Method.; the Atlas 
d’Hist. Nat., of the same work; Desmarest, Consider. Gener. siir la Classe des 
Crust. ; the plates of the Voy. de Freycinet. We should observe that in the figure 
vtf the. Cancer megisfos, Herbst., LXI, 1, the tail is false ; this arises from the fact 
that the tail was wanting in tlic individual from which the drawing was made, the 
artist supplying it by copying the fin-tail of an ordinary Macroura. 
