384 CRUSTACEA 



S. empusa Say (Fig. 615). First antennae with 3 flagella; second 

 shorter and with a very large flat scale (exopodite) ; length up to 25 

 cm.; color greenish-gray: Florida to Cape Cod, in shallow burrows in 

 the mud, between tide lines and in shallow water, each burrow usually 

 having 2 or 3 openings a few feet apart; often very common. 



ORDER 3. CUMACEA. 



Body small, with a small carapace which does not cover the hinder 

 4 or 5 thoracic somites, and with a long slender abdomen; first anten- 

 nae short; second antennae short in the female and long in the male; 

 mandibles without palp; 2 pairs of maxillipeds and 6 pairs of periopods 

 present, 2 to 5 pairs of the latter being biramose (small exopodite pres- 

 ent) ; the pleopods, with the exception of the uropods, wanting in the 

 female, while in the male 2 to 5 pleopods may be present; a single pair 

 of gills on the first pair of maxillipeds; eyes close together and sessile or 

 wanting ; the large eggs are carried by the female in a brood pouch under 

 the foremost free thoracic segments and the hinder part of the cara- 

 pace; the young animals are like the parents in appearance, but are 

 without the last pair of thoracic and all the abdominal legs when born: 

 9 families and about 300 species, all marine and living mostly in the sand 

 and mud. 



FAMILY DIASTYLIDAE. 



With the characters given above: 8 American genera. 



DIASTYLIS Say. Seven abdominal segments present, the telson 

 being well developed and long and pointed; a single eye or none; the 

 3 anterior pairs of periopods in the female 

 and the 5 in the male biramose: numerous 

 species, several American. 



D. quadrispinosa G. O. Sars (Fig. 

 616). Length 10 mm.; body flesh color or Fig * 

 brownish; a short spine projects from the 



carapace on each side a little behind the large triangular rostrum: Nova 

 Scotia to New Jersey in 2 to 200 fathoms; often very common. 



ORDER 4. DECAPODA. 



Shrimps, crayfish, lobsters, and crabs. Thoracostracans in which 

 the carapace covers the entire thorax, the cephalothorax being cylindrical 

 in the Macrura and broad and more or less flattened in the Brachyura; 

 gills on the thorax, extending either from the legs (podobranchs), the 

 joints (arthrobranchs), or the body wall (pleurobranchs) and situated 

 in the gill chamber on each side of the body (Fig. 623) ; abdomen well 



