CAMliAKl'S. 35 



12. Cambarus Alleni. 



Plate I. fig. 1, Plate VIII. HB. 9, it: 



Alli'i/!, F.vvix, Proc. Amer. Acad. Arts ami Scl., XX. 110, 1884. 



Male, form I. Rostrum broad, triangular, somewhat deflexed, smooth, 

 excavated above, margins raised into sharp crests and gradually converging 

 to near the tip, where they suddenly come together to form the short, 

 sharp acumen ; no lateral spines. Post-orbital ridges without spines. Cara- 

 pace cylindrical, somewhat compressed laterally, fore border angulated be- 

 hind the antenna?, punctate above, granulated on the sides. Cervical groove 

 deeply sulcated, without lateral spines. Cardiac region more than one third 

 as long as the distance from the tip of rostrum to hind border of carapace. 

 Areola narrow. Abdomen broad, longer than cephalo thorax. Angles of 

 pleura rounded. Three or four spines on each side of posterior border 

 of basal segment of the telson. Terminal segment of telson shorter than 

 basal part, one third broader than long, hind margin concave. Anterior 

 process of epistoma subquadrangular. Basal segment of antennules with a 

 sharp spine below, near the inner margin, half-way towards the end of the 

 segment. Antennas shorter than the body, second and third segments with 

 an external sharp tooth. Antennal scale equal to peduncle, slightly sur- 

 passing the rostrum, broad, broadest at the middle, rounded at apex, termi- 

 nating in a short spine, external margin inflated. Third maxillipeds hairy 

 within and below. Chelipeds slender, chela long, subcylindrical, squamoso- 

 tuberculate, tubercles ciliate anteriorly, internal border straight, serrate. 

 Fingers as long as the hand, with alternate longitudinal ribs and lines of 

 ciliate impressed dots. Opposed margins of fingers straight, unidentate. 

 Carpus squamoso-tuberculate within, obsoletely so without, with one promi- 

 nent spine on inner border. Meros punctate outside, ciliato-tuberculate 

 within and on upper margin, which has two ante-apical spines obliquely 

 placed ; two rows of spines beneath. Third and fourth pairs of legs hooked 

 on third segments, hooks of fourth pair bituberculate. Fifth pair of legs 

 with a flattened laminate tubercle on basal joint. Anterior abdominal appen- 

 dages of moderate length, bifid at apex, outer part forming a broad flattened 

 plate whose anterior margin is furnished with hairs and one strong seta, the 

 posterior margin of the plate produced anteriorly into a blunt tooth-like 

 process. Inner part bearded within, and produced into a long erect spine, 

 which much exceeds in length the outer part of the appendage. 



