388 CRUSTACEA 



terior part j abdomen sharply bent at the third segment ; length 15 to 26 

 mm. ; color translucent, usually greenish and spotted with red : Vineyard 

 Sound and southwards, common in eel grass. 



6. ALPHETJS Fabricius. First pair of periopods larger than the 

 others and chelate, the right and left claws of the first pair being thick 



and of very unequal size; rostrum small 

 or absent; abdomen not sharply bent; 

 eye stalks short and hidden: about 

 one hundred species, twelve American, 

 living principally along our southern 

 coasts. 



A. minus Say. Rostrum present; 

 hinder feet with spines beneath; length 

 Fig. 621 Mpkeus^heterochelis 4 cm . : Atlantic coast from New Jersey 



to Florida; southern Calif ornian coast. 



A. heterochelis Say (Fig. 621). Large claw with a constriction at 

 its middle; rostrum spiniform; length 5 cm.: Virginia to Florida; 

 California. 



FAMILY 3. PENEIDAE. 



Southern shrimps and prawns. First 3 pairs of periopods chelate, 

 the third pair being the largest ; rostrum long ; second antennae long, with 

 a large scale; abdomen compressed and not bent sharply: about 2 

 American genera, marine, inhabiting chiefly the tropics and the deep sea. 



PENEITS Latreille. Rostrum serrate; eye stalks jointed; the young 

 born as nauplii: 3 American species. 



P. setiferus (L.). A lateral groove on each side of the forward half 

 of the carapace ; flagella of first antennae very short ; length up to 16 cm. : 

 common in shallow water along the coast from Virginia southwards, 

 where it is an article of food, the larger individuals being known in the 

 market as prawns and the smaller as shrimps. 



P. brasiliensis Latreille. Like P. setiferus, but with the lateral 

 grooves extending the length of the carapace: Atlantic coast north 

 to Cape Cod, occurring with P. setiferus. 



TRIBE 2. THALASSINIDEA.* 



Animals of moderate size, with a cylindrical or flattened and trans- 

 lucent body and a large abdomen; carapace with 2 longitudinal sutures; 

 antennal scale usually wanting; first pair of periopods form pinching 

 claws of unequal size: marine, burrowing animals; 3 families and about 

 75 species. 



* See "Synopsis of Astacoid and Thalassinoid Crustacea," by J. S. Kingsley, Am. 

 Nat., Vol. 33, p. 819, 1899. 



