1817.] GENUS ASTACUS. 165 



Genus ASTACUS. 



Antennae inserted in nearly the same horizontal line; 

 six anterior feet didactyle; the anterior pair largest; mid- 

 dle division of the caudal lamellae broader at base; exter- 

 nal division biparted. 



SPECIES. 



1. A. ?narinus. Rostrum two or three- spined; each 

 side, a smaller simple one each side of the base, one more 

 distant on the thorax, one usually beneath near the tip; 

 carpus above five-spined; hand six or nine-spined on the 

 inner edge. 



Astacus marinus americanus. — Seba tom. 3. tab, 17. 

 fig. 3. 



Inhabits the rocky parts of the coast. 



Cabinet of the Academy. 



Bodi/ with numerous, small, unequal, excavated dots; 

 thorax with a dorsal, linear, cicatrice, drawn from near 

 the tip of the rostrum to the base of the abdomen, the last 

 joint of the abdomen with two re . ote fascicles of hairs at 

 tip, lateral ar.glt duplicate beneath; tail, middle division 

 simple, one-spined each side near the tip, a fascicle of 

 hair near the base above, inner latterai lamella one-spined 

 at the external angle, external one with rather acute spines 

 at the junction of the accessory plate, outer margin rugose; 

 colour, when recent, olivace ) is- black, with darker spots, 

 and varied with yellowish bands, beneath and tips of the 

 spines orange-red. Caudal cilia iulvous. 



Length 



Seba appears to have been the only naturaUst who 

 has considered this species as distinct froni the very prox- 



