32 NEW-YORK FAUNA CRUSTACEA. 



This is abundant in winter on our coast. It is called Opossum Shrimp in England, from 

 the circumstance that it carries a sac under the thorax, in which the eggs are hatched, and 

 where they are carried for some time. It is supposed by more recent writers to be the males 

 only which carry the young in pouches after exclusion, similar to what has been observed in 

 the family Syngnathidce among the fishes. It is also stated to migrate regularly into fresh 

 water, but I have had no opportunity of verifying the fact. It occurs on both sides of the 

 Atlantic. 



(EXTRALIMITAL.) 



Genus Diastylis, Say. Thorax smooth, six-jointed ; the anterior larger than all the others, com- 

 pressed and rostrated ; the four antenna? placed on the same plane. Five pairs of bifid feet ; 

 the anterior truncated. Abdomen five-jointed ; the first and second with natatory feet. Tail 

 with a single bifid style on each side of the first segment. 



Obs. I place this genus where it was supposed by its author to belong. He did not observe 

 the eyes, which he says were probably retractile. All the species of this order, hitherto ob- 

 served, have pedunculated eyes. It may possibly be the young of some other crustacean. 

 D. arcnarius. (Say, loc. cit. p. 314.) Thorax minutely crenate on the anterior portion of the sides. 

 Lateral caudal styles divaricated, longer than the tail; terminal style less than half the length of 

 the lateral ones. Length, 0-2. Pools on the coast of Georgia and Florida. See Montagu, 

 Linnean Transactions, Vol. 7, pi. 6, for C. scorpoides, which Mr. Say thinks a congeneric 

 species. 



GENUS SQUILLA. Fabricius. 



Shield divided into three lobes. Lateral appendix of the three last pair of thoracic feet slen- 

 der and pointed. External antennae terminating in a broad oval ciliated plate. Second pair 

 of jaw-feet expanded into large lamellar hand-claws, stoutly toothed on the edges. 



Squilla empusa. 



PLATE XIII. FIG. 54. 



(STATE COLLECTION.) 



Squilla empusa. Say, Jour. Acad. Nat. Sciences, Vol. 1, p. 250. 



S. id. Milne-Edwards, Hist. Nat. cles Crustaces, Vol. 2, p. 525. 



Description. Thorax narrowed in front, dilated behind, and deeply concave on the posterior 

 margin. Surface with a medial longitudinal ridge, and two on each lateral lobe ; the interior 

 short, the exterior terminating abruptly before it reaches the posterior rounded termination : an 

 obtuse angle on the side of this lobe, which is not very obvious in the desiccated specimen. 

 Anterior margin with slightly prominent spines. Last joint of the hand-claw slender, with 



