ORDER DECAPODA. 181 



or cephalic division in the form of a heart. {Pagurus clypea- 

 tus, Fab.) 



Those which form the most numerous division, Pagurus, 

 proper, Lat?'., have, on the contrary, the middle antennae 

 curved, notably shorter than the lateral, with the two threads 

 short, and the upper one in an elongated or subulated cone. 

 The anterior division of the thorax is squared, or in the form of 

 a triangle inverted and curvilinear, {Cancer Bernhardus, 

 Linn.) 



A species inhabiting the Mediterranean should, from its 

 peculiar characters, form a subgenus proper (Prophylax, 

 Latr.) In these the tail, instead of being, with the exception 

 of the upper of the three last segments, soft and arched, and 

 having but a single rank of oviferous threads, is covered with 

 coriaceous teguments, is directed in a straight line, and is not 

 curved underneath, except at its extremity. Its inferior sur- 

 face presents a furrow, and two ranks of false feet. The body 

 besides is linear, with two lateral appendages at the end of 

 the tail almost equal, and whose division is larger, foliaceous, 

 and ciliated. The last four feet are slightly granular at their 

 extremity, and appear to be terminated only by a single finger, 

 or at least are not very distinctly bifid. Perhaps we must re- 

 fer to this division, the paguri living in serpulae, alcyones, &c. 



In all the following macroura, the two posterior feet at most 

 are alone smaller than the preceding. Most frequently the 

 false subcaudal feet are five pair in number. The teguments 

 are always crustaceous. The lateral fins of the penult seg- 

 ment of the tail, and its last one, form one in common, dis- 

 posed like a fan. 



The two following sections have a common character, which 

 separates them fi'om the fourth. The antennae are inserted at 

 the same height, or on a level. The peduncle of the lateral 

 ones, when it is accompanied with a shell, is never entirel}' 

 covered by it. The false sub-caudal feet are often but four iu 



