CRAYFISHES. 353 



branchial formula is the same as in the genus Cheraps, and essentially the same 

 as in Paranephrops; but according to Nobili the podobranchiae of the eighth 

 and ninth somites are not furnished with an ala or lamina in the genus Astacone- 

 phrops, whereas in the genus Cheraps these podobranchiae are alate. 



Parastacus araucanius, sp. nov. 

 Plate 4. 



Male: — Cephalothorax shorter than the abdomen, strongly compressed 

 laterally, mostlj' smooth, minutely granulated on the sides; areola broad (about 

 two thirds as broad as long), minutely punctated; rostrum short, not reaching 

 the distal end of the second antennulary segment, margins elevated, slightly 

 convergent from base to near the tip, where they abruptly converge to form the 

 abbreviated acumen; the infero-lateral edges of the rostrum are visible from 

 above, forming the superior border of the orbit separated from the supero-lateral 

 edge of the rostrum by a groo^•e; distal half of the rostrum concave above; 

 antero-lateral margins of the carapace produced into a prominent, rounded 

 angle below the small eye which Ues in a deep and uncommonly complete orbit. 

 Post-orbital ridges, obsolete. The pleural angles of the abdomen are rounded, 

 the telson long with a pair of lateral spines and a longitudinal median furrow on 

 its upper face along its distal half; the median rib on the upper side of the inner 

 branch of the last pair of abdominal appendages ends in a small spine situate 

 a little distance from the margin. Antennal scale short and broad. The 

 chelipeds are asymmetrical, the right one being the larger; the meros is tuber- 

 culated on its lower face, granulate on the superior margin, but destitute of 

 spines; the surface of the carpus is Ughtly squamoso-granulate, the granulations 

 becoming more pronounced on the supero-interior edge where they take the form 

 of blunt tubercles; the chela, too, is lightly squamoso-granulate, without any 

 prominent spine or tubercle, except one blunt tubercle or tooth near the base of 

 the immovable finger; the superior and inferior borders are rounded. 



Dimensions. Length, 42 mm.; length of cephalothorax, 19 mm.; length 

 of areola, 6 mm., breadth of areola, 4 mm.; length of larger claw, 15.5 imii., 

 breadth of do., 7 mm., length of dactylus, 8.5 mm. 



Corral, Chile, Dec. 18, 1908, in a cascade stream. Thomas Barbour coll., V 



M. C. Z., No. 7,355. 



This species is related to P. nicoleti (Phil.) and P. hasskri Fax. Like these it 

 has a strongly compressed cephalothorax, indicating a burrow-dwelling species. 



