68(3 PROCEEDINGS OF THE NATIONAL MUSEUM. 



of the thirteenth somite is reduced to a small, simple filament. The 

 podobranchiae are alate and the aire are provided with hooked tubercles 

 similar to those of the Astacince. The coxopoditic setae are long and 

 hooked at the end. 



Habitat.— Colima, Mexico. J. Xantus. (No. 4133, Coll. TJ.S.ET.M.) 

 One specimen. 



The locality is notable as being the only one north of the equator 

 where Parastacine crayfishes occur. Furthermore, the close affinity 

 between this species and a native of Uruguay (Parastacus saffordi) is 

 surprising. But beyond this there appears to be no reason to discredit 

 the legend which accompanies the type specimen of P. varicosus in the 

 United States National Museum. 



PARASTACUS DEFOSSUS, new species. 



(Plate LXVII, figs. 3,4.) 



Cephalo-thorax laterally compressed, the sides high and nearly vertical. 

 Anterior segment of abdomen small. Rostrum small, triangular, deflexed, 

 plane above, lateral borders slightly marginate, strongly converging from 

 the base to the blunt tip which hardly reaches to the proximal end of the 

 third antennular segment. The margins of the rostrum are prolonged 

 backward for a short distance on the gastric area, where they tend to 

 fuse with the anterior end of the postorbital ridges. The latter are 

 but slightly marked, unarmed, strongly divergent in their backward 

 course. The suborbital angle is prominent, but perfectly rounded off. 

 The dorsal surface of the carapace is smooth, polished, and sparsely 

 punctate, the lateral walls lightly granulate. The areola is very long 

 and narrow, the gastric area proportionally short. Abdominal pleurae 

 rounded, telson long, posteriorly oval in outline. Anterior process of 

 epistome rather long, but slightly separated from the body of the 

 epistome by transverse suture; anteriorly truncate. Antennae about 

 equal in length to the cephalo-thorax; scale small, broad, broadest 

 near the distal end, external border terminating in a long, stout spine 

 directed a little outward; a blunt spine or tubercle on the lower side of 

 the first antennal segment, just in front of the orifice of the green 

 gland; no external spine at base of the scale. Third maxillipeds hairy 

 within. Chelipeds symmetrical ; merus trigonal, outer face smooth, infe- 

 rior edges serrate, superior edge armed with one blunt tooth near the 

 distal end; carpus broadly triangular, internal border armed with a 

 single series of blunt teeth which increase in size toward the distal end 

 of the segment; hand short and broad, the palm as broad as long, outer 

 face convex, smooth, with scattering coarse puncta, superior (or internal) 

 margin ornamented with a low crest of squamous, setiferous tubercles, 

 inferior border similarly adorned with single row of tubercles running 

 from the proximal end of the hand as far as to the base of the immo- 

 bile finger, where they are replaced by shallow pits; dactylus equal in 

 length to the breadth of the hand, upper margin rounded, with a single 



