PROC. BIOL. SOC. WASH. 104(2), 1991, pp. 309-316 PROCAMBARUS (GIRARDIELLA) STEIGMANI, A NEW CRAYFISH (DECAPODA: CAMBARIDAE) FROM A LONG-GRASS PRAIRIE IN NORTHEASTERN TEXAS Horton H. Hobbs, Jr. Abstract.— Procambarus {Girardiella) steigmani, a crayfish which appears to be a habitual (primary) burrower, is described from a single locality on the Parkhill Prairie, in the Trinity River watershed of Collin County, Texas. Its closest relative, from which it differs in possessing asymmetrical first pleopods in the male and a highly sculptured annulus ventralis in the female, is P. (G. ) regalis which has been reported from the Ouachita and Red river basins of southwestern Arkansas. Described herein is Procambarus (G.) steigmani, the third previously undescribed member of the subgenus Girardiella to be recognized since Hobbs & Robison (1988) reviewed the occurrence of the genus in Ar-kansas and presented a key and illustrations to aid in the recognition of the 10 then-known members of the gracilis group of the subgenus. Procambarus (G.) kensleyi and P. (G.) nigrocinctus, both rather distantly re-lated to P. (G.) steigmani, were subsequent-ly described by Hobbs (1990) from the Neches River basin of eastern Texas. The new species is closely allied to P. (G.) regalis Hobbs & Robison, 1988, from southwest-em Arkansas, sharing so many features in common with that species that I am tempt-ed to recognize it as a subspecies of the lat-ter. Until more is known about the ranges of the two, the treatment proposed here seems to me, however, to be based on fewer assumptions. An error is present in the key mentioned above (Hobbs & Robison 1988:404): at the end of couplet 2, "6" should read "7" and, at the end of couplet 5, "6" should replace "7." Using this key with the corrections not-ed, P. (G.) steigmani would be identified as P. (G.) regalis from which it may be distin-guished readily by its possessing asymmet-rical first pleopods, a feature apparently unique in the subgenus. Procambarus (Giradiella) steigmani, new species Figs. 1, 2 Crayfish.— Eig, 1990:1 A, 5 A, unnum-bered color photograph. Diagnosis. —Body pigmented, eyes well developed. Rostrum lacking marginal spines, tubercles, and median carina. Car-apace without cervical spines or tubercles. Areola often linear but never less than 45.5 times as long as wide and constituting 37.4 to 41.9 (JT = 40.1) % of total length of car-apace (44.6 to 47.6, X = 46.0% of postor-bital carapace length). Suborbital angle weak and obtuse. Hepatic and mandibular areas weakly tuberculate; branchiostegal spine absent. Antennal scale about 2.4 times as long as broad, widest distal to midlength. Ventral surface of palm of chela punctate mesially and laterally (rarely with single small tubercle ventromesially), no tubercles on ventral surface of dactyl. Ischium of third pereiopod of first form male with simple strong hook overreaching basioischial artic-ulation; hook not opposed by tubercle on corresponding basis; coxa of fourth pereio-
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