656 PROCEEDINGS OF THE NATIONAL MUSEUM. 



CAMBARUS DIFFICILIS, new species. 

 (Plate LXV, figs. 1-4.) 



Cephalo-thorax oval, flattened above, of equal length with the abdo- 

 men. Carapace obscurely punctate above, lightly granulate on the 

 sides; lateral spines of moderate size, branchiostegian spines obsolete, 

 anterolateral margins but slightly and bluntly angulated, unarmed 

 with spines. Eostrum of moderate length, reaching a trifle beyond the 

 proximal end of the third antennular segment; upper surface excavate, 

 margins convergent and slightly convex from the base to the single 

 pair of lateral teeth, which are small and acute, with horny tips; 

 acumen of moderate length, acute, horny at the slightly upturned tip. 

 Postorbital ridges ending anteriorly in a sharp tooth or short spine. 

 Areola obliterated throughout a considerable part of its length by the 

 contiguity of the branehio-cardiac lines. Abdominal pleurae rounded, 

 telson bispinose on each side. Anterior process of epistome squarely 

 truncate at the front end. 



Antennas longer than the body, basal segment unarmed, second seg- 

 ment furnished with a spine on the outer side, at the base of the scale; 

 scale ol* moderate width, widest near the middle. 



The merus of the chelipeds shows the usual biserially arranged spines 

 upon its lower side, and the two obliquely placed spines near the distal 

 end of the upper margin; the carpus is marked by a deep, curved 

 longitudinal furrow on the upper side, just inside of which lies a series 

 of about seven small tubercles, the anterior one sharp pointed and quite 

 near to the upper point of articulation with the propodite; the inner 

 border of the carpus is armed with a stout median spine and a smaller 

 one near the hinder end of the segment; on the lower face of the seg- 

 ment one sees a minute spine at the lower articular surface with the 

 propodite, a prominent median spine, and a much smaller one between 

 the inferior median and the larger spine of the inner border; the chelae 

 are very large, a little longer than the cephalo-thorax including the 

 rostrum; the palm or basal part is short, its inner border ornamented 

 with a double row of dentiform tubercles, outside of which, on the 

 upper face, appears a row of obsolescent tubercles in line with the 

 axis of the movable finger; the fingers are very long (the movable one 

 being from two and a half to a little over three times the length of the 

 inner border of the palm), pitted and furrowed, armed with blunt teeth 

 along their prehensile edges; the inner border of the dactylus is fur- 

 nished with dentiform tubercles which show a tendency to an arrange- 

 ment in two rows, and which decrease in size from the proximal to the 

 distal end of the segment; it is further to be observed that the dactylus 

 is bowed inward in such a fashion that the prehensile edge comes into 

 contact with the immovable finger throughout the distal two-thirds of 

 its length when the fingers are closed, leaving a gape at the base. 



The upper surface of the hand and wrist is mottled with dark spots. 



