240 CRUSTACEA OF THE UNITED STATES. flMay. 



and contracted each side in the middle; natatory appen- 

 dices attached to the third, fourth and fifth segments, 

 composed each of a semilunate plate, with an incurved 

 fin attached to the anterior lateral base, which when at 

 rest is placed on the anterior face of the plate, and the 

 plate when at rest is incumbent forwards; tail rounded at 

 tip, contracted towards the base, and about two thirds the 

 length of the preceding segment; lateral lamellce simple, 

 longer than the tail, inner one linear, comose, exterior 

 one dilated, triangular, ciliated at tip. 



Inhabits the coasts of the southern states and of East 

 Florida. 



Cabinet of the Academy. 



Length of the specimen four and a half inches. 



The exuviae of this singular animal, particularly of 

 the large anterior foot, occurs very frequently on the sea 

 beach of the southern states early in the spring. It is 

 rarely seen, owing to its recluse mode of life. We found 

 this specimen by digging in the sand of the bay shore 

 of the river St. John in Kast Florida, about eighteen 

 inches below the surface, near low- water mark; it had 

 formed a tubular domicil, which penetrated the sand in 

 a perpendicular direction to a considerable depth, the 

 sides were of a more compact consistence than the 

 surrounding sand, projecting above the surface about 

 half an inch or more, resembling a small chimney, and 

 rather suddenly contracted at top into a small orifice. 

 The deserted tubes of the Callianassa are in many places 

 very numerous, particularly where the sand is indurated 

 by iron into the incipient state of sand- stone; they are al- 

 ways filled up, but may readily be distinguished by the 



