Thelycum of female with anterior margin of 

 median plate and lips of transverse groove evenly 

 rounded, notched in middle; lateral flaps of last 

 thoracic somite overlapping median plate; rib 

 supporting expanded median plate extending 

 anteriorly and sharply set off from anterior ven- 

 tral margin of plate; ventral surfaces pubescent. 

 Sternal elevation between coxae of fifth leg of 

 male with lateral margins indented setting off 

 posterior portion from broad anterior basal por- 

 tion; petasma with distolateral corners greatly 

 produced as hornlike projections. 



Measurements. — Length of body : 92 mm. 



Color. — Translucent with purplish-gray 

 blotches ; appendages pink. 



Habitat. — Primarily sand or mud and shell 

 bottom in high-salinity water; shallow water to 

 30 fathoms. 



Type locality. — Beaufort, N.C. 



Known range. — Tangier Sound, Chesapeake 

 Bay, to Texas; Bermuda; Puerto Rico and 

 Sombrero Island; Surinam. 



Remarks. — Eldred (1959) reported T. con- 

 strictus as common in the Tortugas area of Florida 

 where, along with its near relative, T. similis, it 

 makes up about 7 percent of the annual commer- 

 ( cial catch. It probably contributes more to catches 

 in deeper water than to catches in the area 

 sampled. Gunter (1950) stated that T . constrictus 

 was rarely taken in coastal bays of Texas, 

 being largely confined to water above 30°/ oo . 

 In littoral waters, ripe females were taken in 

 September and small specimens (about 29 mm. 

 total length) in March. 



Burkenroad (1939) remarked that T. con- 

 strictus might be restricted largely to sandy 

 bottom, and Hildebrand (1955) suggested a dis- 

 tribution possibly correlated with bottom type, 

 but did not specify the type. 



The early developmental stages of T. constrictus 

 were treated by Pearson (1939). All larval and 

 postlarval stages were pieced together by success- 

 ful rearing techniques coupled with plankton 

 catches at St. Augustine Inlet, Fla. Descriptions 

 were given of the egg (from the two-cell stage 

 onward), five naupliar, three protozoeal, two 

 mysis, and early postlarval stages. A year-round 

 spawning season is indicated, because eggs were 

 taken at St. Augustine, Fla., from April to 

 August, and at Fort Pierce, Fla., in summer and 



from December to February. Nauplii were found 

 from April to August, and the remaining stages 

 from May to August, with a few protozoeae being 

 taken also in winter. Pearson found develop- 

 mental stages of this species more abundant than 

 those of related species in shallow oceanic water; 

 in estuarine water the postlarvae were rare. He 

 attributed this rarity and the comparative scarcity 

 of adults in commercial catches to the burrowing 

 habits of postlarvae and adults, as observed in the 

 laboratory. Somewhat contrary to Pearson's find- 

 ings, the juvenile stages of this species have been 

 caught commonly in surface plankton tows made 

 with a coarse-mesh net on nightly flood tides in 

 Bogue Sound near Beaufort Inlet, N.C. These 

 collections have been made in summer and fall 

 (mid-June to mid-November) when salinities 

 ranged from 28 to 36 % . 



Subfamily Sicyoninae 



Body more or less sculptured and rigid, with 

 prominent, often more or less interrupted dorsal 

 carina. Carapace with or without spine at anten- 

 nal angle. Lateral section of ocular somite de- 

 veloped into elongated stylet. Basal antennular 

 article lacking enlarged ciliated protuberance 

 (prosartema) on inner proximal margin. No 

 pleurobranchs behind ninth somite (third maxil- 

 liped). Fourteenth somite (fifth legs) without 

 gills. Pleopods lacking endopods except in modi- 

 fied form on first and second j)leopods of male 

 ( modified after Burkenroad, 1931b ) . 



Burkenroad (1934b) pointed out that the sub- 

 family Sicyoninae is an extremely uniform group. 

 Unlike other penaeids, sexual maturity may be 

 attained at a quite small size. "Differences be- 

 tween small and large individuals of any species 

 are slight and chiefly affect rostral length, eleva- 

 tion and distal armature, these features in 

 general becoming respectively shorter, more 

 horizontal, and with more numerous distal teeth 

 as size increases, and the armature of the pleonic 

 [abdominal] pleura, which generally increases in 

 strength and extent with growth." The thelycum, 

 and corresponding male genital sternites, are less 

 varied than among other penaeid groups, and, 

 consequently, are not so serviceable in distinguish- 

 ing species. The serious student is referred to 

 Burkenroad (1934b, pp. 70-76) for full discussion 

 of these characters. 



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