NO. 1136. OBSERVATIONS ON THE ASTACID.E— FAXON. 645 



not obliterated and the sides of the rostrum are less strongly conver- 

 gent. This is without doubt to be considered the typical form of 

 C. clarkii, since Girard's specimens were collected in the same region, 

 somewhere between San Antonio and El Paso del Xorte. 



CAMBARUS ACHERONTIS Ldnnberg. 



(Plate LXII, figs. 1-5.) 



CamharuR acherontis L6nnberg, Zoolog. Anz., XVII, pp. 125-127, 1894; Bibang 

 till K. Sveuska Vet.-Akad. Handlingar, XX, Pt. 1, p. 6., figs. l-(), 1894. 



Female. — Rostrum broad, excavated, superior lateral margins raised 

 into sharp carinoe which overhang the inferior lateral margins and con- 

 tinue backward inside of and parallel with the i^ostorbital ridges 5 a 

 pair of sharp projecting angles or teeth near the tij) at base of the acu- 

 men; acumen short, acute. Rostrum, gastric region, and areola smooth 

 and polished; sides of carapace thickly studded with small papilht or 

 tubercles; postorbital ridges furnished with a small spine at the ante- 

 rior end; areola almost obliterated in the middle by the apposition of 

 the branchio cardiac lines; i)osterior section of carapace equal in length 

 to the distance between the cervical groove and the anterior sj^ines of 

 the postorbital ridges. 



Abdomen a little longer than the cephalo-thorax, smooth; telsou 

 three or two spined on each side of the anterior segment, posterior 

 segment subtruncate. 



Antennie very long, much longer than the body; a small external 

 spine behind the base of the antennal scale; antennal scale very broad, 

 broadest at the middle, apical end rounded and armed with a small 

 external spine. Epistome short, broad, anterior border convex. 



Ohelipeds slender; merus furnished with the customary biserial spines 

 below, superior margin spinulose, outer and inner faces sparsely granu- 

 lated; carpus with a longitudinal furrow above, tuberculiferous, the 

 tubercles tending to assume the form of short si)ines on the inner side; 

 chehe subcylindrical, granulated, the granules on the inner or upper 

 margin of the hand taking on the form of blunt spines; lingers long, 

 slender, inner and outer sides costate, uijper margin of the dactyhis 

 tuberculate, cutting edges of lingers irregularly denticulate on the 

 proximal half. 



Length 75 mm.; carapace 39 mm.; from tip of rostrum to cervical 

 groove 23.5 mm. ; from cervical groove to posterior border of carapace 

 10 mm. ; length of rostrum from tip to anterior spines of postorbital 

 ridges 9 mm.; width of rostrum 4.5 mm. 



Auuulus ventralis transverse, with a prominent posterior tubercle 

 and a crescentic anterior fossa. 



In a young male of the second form, 43 mm. in length, the third pair 

 of legs are furnished with a blunt hook on the third segment, while 

 the corresponding segment of the fourth pair bears a small tubercle, 

 the vestige of the hook of the adult. The lirst abdominal appendages 



