174 CRUSTACEA. 



to the Gecarcin trois-epines, Desmar., a fossil species, Hist. Nat. 

 des Crust. Foss., VIII, 10 ; he suspects it may belong to the genus 

 Thelphusa. 



Here, at least in the females, the shell is very thin, membranous, 

 and flexible, and the body almost round or subovoid. The ocular 

 pedicles are sensibly shorter than in the preceding subgenera. First 

 comes the 



MiCTYRis, Lat. 



\'^Tiere the body is subovoid, highly inflated, narrower, and more 

 obtuse before, and truncated posteriorly; the clypeus considerably 

 diminished, and its extremity narrowed into a point. The claws form 

 an elbow at the junction of the third and fourth joint, the latter of 

 which is almost as large as the hand ; the other feet are long, with 

 angular tarsi. To these essential characters we will add, that the 

 ocular pedicles are curved, and crowned with globular eyes ; that the 

 external foot-jaws are verj' ample, and their internal edge hairy, the 

 second joint being very large, and the following one almost semi- 

 circular. 



Two species are known : one is found in the Australasian 



Ocean*, and the other in Egypt t, where it was observed by M. 



Savigny. Immediately after these come the 



Pinnotheres, Lat. 



Very small Crustacea, which during a part of the year, in Novem- 

 ber particularly, inhabit various bivalve shells, chiefly the Mytili and 

 Pinnae. The shell of the females is sub-orbicular, very thin and soft, 

 while that of the males is solid, almost globular and somewhat nar- 

 rowed into a point before. The feet are of a middling length, and 

 the claws straight and formed as usual. The external foot-jaAvs pre- 

 sent but three distinct joints, the first large, transversal, and arcuated, 

 and the second furnished at its internal base with a small appendage. 

 The tail of the female is very ample, and covers the whole under part 

 of the body. 



The ancients believed that they resided with the MoUusca, in whose 

 shells they are found, on friendly terms, warning them of danger and 

 seeking food for them. The inhabitants of certain districts, at the 

 present day, attribute to their presence the unwholesome qualities 

 sometimes manifested in the Mytili |. 



We now arrive at Crustacea, which, although analogous to those 

 just mentioned in the insertion of their ocular pedicles, are removed 

 from them in respect to their shell. It is heart-shaped, and trunca- 

 ted posteriorly, elevated, dilated and rounded on the sides near the 

 anterior angles. The ocular pedicles are shorter than those of the 



* Lat., Gener. Crust, et Insect., I, 40 ; Encyc, Method., Atlas d'Hist. Nat. 

 ccxcvii, :i ; Desmar., Consider., XI, 2. This subgenus, and that of the Pinnotheres, 

 in the first edition of this work, constituted part of the Orbiculavia ; but in their 

 natural order they approach the Ocypodes, Gecarcini, &c. 



t PI. d'Hist. Nat., of the great work on Egypt. 



X For species see Leach, Malac. Podoph. Britt., and Desmar., Consider. Gf^ncr. 

 sur les Crust., 1 16. 



