168 GENUS ASTACUS: [Decembei. 



known by the name of Craw-fish or Fresh-water lobster; 

 with many it is esteemed as a delicious food, though not 

 much sought after, but in some parts of the country, chil- 

 dren eat them aUve, or only their claws. It was first de- 

 scribed as distinct from the fiuviatilis by Mr. Bosc, who 

 named it in honour of the late professor B. S. Barton. 



3' A. affinls.^ Rostrum mucronate, subcanaliculate, 

 two-spined; a spine behind each eye, and a larger gemi- 

 nate one, on each side of the thorax; hand and thumb on 

 the inner edge scabrous. 



Inhabits the river Delaware. 



Cabinet of the Academy. 



Sody and extremities with scattered distinct punctures, 

 which are not conspicuously larger on the hands, all fur- 

 nishing hairs, from one to four in each; thorax with 

 a double, prominent, acute spine each side, behind the 

 transverse arcuated band, which is deeply impressed, and 

 terminated on the anterior lateral edge, at an acute spine; 

 a spine on the peduncle of the base of the scale, and a 

 moveable one at the base of the second joint of the pedun- 

 cle of the exterior antenna; interior antenna with a pro- 

 minent spine on the first joint of the peduncle beneath; a 

 group of four or five spines between the base of the exte- 

 rior attenna and the double spine; rostrum acutely spinose 

 each side near the tip, tip attenuated into an acute spine, 

 which rather surpasses the tip of the third joint of the pe- 

 duncles of the interior antennse, abbreviated carina each 

 side of the base, elevated, and terminated behind the eye 

 in a spine; anterior f vet, third joint with a double series 

 of spines beneath, two above placed obliquely, two smaller 

 ones at tip, and one behind the outer condyle; carpus 



