DECAPODA. 35 



placed among the Ocypodes, under the specific name of quadriden- 

 tata, a crustaceous animal, which appears to us to bear a close re- 

 semblance 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. 



Where the body is subovoid, highly inflated, narrower and more 

 obtuse before, and truncated posteriorly; the clypeus considerably di- 

 minished, 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 very 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(l), and the other in Egypt(2), where it was observed by 

 M. Savigny. Immediately after these come the 



Pinnotheres? Lat. 



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

 ber particularly, inhabit various bivalve shells, chiefly the Mytili 

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

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

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

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

 present 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 Mollusca, in 



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

 ccxcvii, 3; Desmar., Consider., XI, 2. This subgenus, and that of Pinnotheres, in 

 the first edition of this work, constituted part of the Orbicularia; but in their nat- 

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



(2) Pi. d'Hist. Nat., of the great work on Egypt. 



