80 A REVISION OF THE ASTACIDA. 
31. Cambarus cornutus. 
Plate V. figs. 1, 2, Plate IX. figs. 3, 3’. 
Cambarus cornutus, Faxon, Proc. Amer. Acad. Arts and Sci., XX. 120, 1884. 
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 suleate 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, with 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. Antennz longer than the body, flagellum 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. Chelipeds 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 ; 
external finger serrate 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 
