188 
CLASS CRUSTACEA. 
moreover, is much more considerable. The peduncle of the 
lateral antenna is accompanied with a scale, or spines ; the 
external leaf of the lateral fins of the end of the tail is, in ah 
the living* species, as it were, divided into tw'O by a transverse 
suture. 
Eryon, Desm., 
Have all the leaflets of the caudal fin, narrowed at their ex- 
tremity, and terminating in a point ; the exterior one presents 
no transverse suture ; the two threads of the middle antennae 
are very short, and scarcely longer than their peduncle ; the 
sides of the testa have very deep notches ; the forceps of 
the two anterior claws are narrow' and elongated. ( Eryon 
Cuvierii , Desm., a fossil species.) 
Astacus, Gronov ., Fab , 
Have the leaflets of the lateral fins of the end of the tail 
w idened and rounded at their extremity ; the external one is 
divided transversely into two by a transverse suture, the pos- 
terior extremity of that of the middle is obtuse or rounded; 
the tw r o threads of the middle antennae are notably longer than 
their peduncle ; the sides of the testa are not incised. 
In some, and all marine, the last segment of the tail, or that 
which occupies the middle of the terminal fin, presents no 
transverse suture. 
Those whose lateral antennae have a large scale on the 
peduncle, whose eyes are very large, and kidney-formed, and 
in which the pincers of the tw r o anterior claws are narrow, 
elongated, prismatic, and equal, form the genus Nephrops 
of Dr. Leach. ( Cancer Norwegians, Linn.) 
Those in which the peduncle of the lateral antennae presents 
simply but two short projections, in the form of teeth or 
spines, whose eyes are neither very large nor reniform, and 
which have the pincers or forceps more or less oval, com- 
