1818.] ^ OF THE UNiTED STATES. 399 



depressed, rounded at tip, not carinated, edge ciliate, 

 nearly equal to the length of the four preceding joints 

 conjunctly, inner lamella of the latteral appendices trian- 

 gular, hind edge but little oblique, ciliated, and mucro- 

 nate at the outer tip, outer lamella oblong-oval, ciliated on 

 the inner edge and two- spine d at tip. 



Length half an inch. 



Taken in St. John's river, Florida, on the Sheeps- 

 head [Sci^na ovicephalus, Bloch.)f Belongs to the genus 

 .^ga of Dr. Leach. 



6. C. immersa*. Head subquadrate; thorax^ first 

 segment profoundly emarginate for the reception of the 

 head. 



Inhabits ^. 



Museum of South Carolina, and Richmond museum- 



Head transversely subquadrate, somewhat narrowed 

 to the tip, which is truncated; body, anterior segment 

 very large, profoundly emarginate for the insertion of the 

 head, the lateral processes rounded at tip and nearly at- 

 taining the transverse line of the clypeus, with a conside- 

 rable interval between the tip and the anterior angle of 

 the head; third and fourth segments longer behind, 

 2ibo\t', fifth segment widest; y^d"^, large joint of the fourth 

 pair extended behind into a spine, that of the diree pos- 

 terior pairs obtusely produced behind, nails rather small; 

 abdomen abruptly much narrower than the thorax; tail,^ 

 terminal segment large, membranaceous towards the tip, 

 lateral appendices very short. 



Length nearly one inch and three fourths- 



t This well known species has rec«flUy been described by Dr.S. L. Mitch- 

 iU under the name olf S. oais. 



