80 A REVISION OF THE ASTAC1 DM. 



31. Cambarus cornutus. 



Plate V. tigs. 1, 2, Plate IX. Hgs. 3, 3. 



•un cornutus, Faxon, Proc. A.iner. Acad. Axts and Sci., XX. 120, L88 I 



Male, form I. — Rostrum long, narrow, excavated above; margins diver- 

 gent at the base, thickened, concave, costate ; acumen long, with upturned 

 horny tip ; lateral teeth at base of acumen upright, stout, blunt, horny. Post- 

 orbital ridges sulcate on the outer side, with well-developed horny-tipped 

 anterior spines. Carapace flat, smooth and punctate above, granulated on the 

 sides; a depression on each side just outside the orbital ridges; no sub-orbital 

 angle nor spine ; cervical groove sulcated, sinuate, with a strong, sharp lat- 

 eral spine ; no branchiostegian spine ; areola long, of moderate width, plane, 

 punctate, widening at the posterior end of the carapace. The length of 

 the areola is equal to the distance from the cervical groove to the base of 

 the rostrum. Abdomen broad, as long as the cephalothorax without the 

 acumen of the rostrum, pleura triangular, Avith sharp lateral angles. Termi- 

 nal segment of telson broader than long, posterior border rounded ; anterior 

 segment of telson bispinous on each side. Anterior process of epistoma very 

 broad, short, triangular ; apex not truncated nor notched. Thoracic sterna 

 ciliated. Basal segment of antennule with a spine on lower side on the distal 

 half of the segment. Antennae longer than the body, tlagcllum very large, 

 composed of annulations flattened in the vertical direction, conspicuously 

 bearded along the inner margin. Antennal scale oblique to the horizontal 

 plane of the body, a little longer than the rostrum, inner margin straight 

 and parallel with the outer margin, subtruncate at the tip. apical spine 

 strong, long and acute ; second segment of antenna with a large external 

 spine at base of the scale; another small but well-formed external spine 

 on the following segment below. Clielipeds large. Chela of moderate size; 

 hand smooth, punctate, internal margin serrate; fingers of moderate length, 

 curved slightly downwards, ribbed and punctate above, tips incurved, horny; 

 externa] finger senate on outer margin, impressed above and below at base; 

 inner borders of fingers tuberculate and ciliated especially at their bases. 

 Carpus smooth, lightly punctate above, with a strong median internal spine 

 and a small basal internal spine ; a sharp, prominent median anterior spine 

 beneath. Meros smooth, a single acute ante-apical spine on the superior 

 margin, only one or two distal spines in the outer row of biserial spines 



