OBSERVATIONS ON THE AST ACID Jl— FAXON. 685 



PARASTACUS VARICOSUS, new species. 

 (Plate LXIX.) 



Similar to P. saffordi, but different in the following particulars : The 

 branchio-cardiac lines bounding the areola are elevated so as to form 

 very prominent, rounded ridges, serrated externally ; these ridges run 

 a short distance down the cervical groove in front, but cease before 

 reaching the hind border of the carapace. The cheliped is very much 

 longer than in P. saffordi; the distal end of the merus, which in the lat- 

 ter species only reaches to the subocular angle, in P. varicosus attains 

 to the level of the rostrum; the hand, too, is very much longer, and 

 different in outline, the superior and inferior margins being straight 

 instead of convex, while the external face is beveled off so as to form 

 a nearly flat field, oblique to the vertical plane of the hand, on each 

 side of a low, blunt, longitudinal keel, which runs from the carpal 

 joint to the base of the thumb. In P. saffordi the superior and inferior 

 margins of the hand are distinctly convex, the external face swollen 

 and roundish. The dorsal surface of the rostrum is conspicuously 

 pitted in P. varicosus, obscurely or not at all pitted in P. saffordi. 

 The anterior ventral margin of the proximal antennal segment is armed 

 with two spines in the former species ; one of these spines lies in front 

 of the orifice of the green gland, the other at the external angle of the 

 segment. In P. saffordi only one of these spines exists — the one at 

 the external angle of the segment. The posterior border of both 

 branches of the swimmerets has a more truncate outline in P. varico- 

 sus than in P. saffordi. 



Length 100 mm.; carapace 49 mm.; from tip of rostrum to cervical 

 groove 34 mm.; from cervical groove to posterior border of carapace 

 15 mm.; abdomen 52 mm.; width of areola 5 mm.; cheliped 91 mm.; 

 merus 24 mm.; length of chela 40 mm.; breadth of chela 13 mm.; 

 length of dactylus 22 mm. 



The number and arrangement of the branchial organs are exhibited 

 in the subjoined table: 



abthkobranchlje. 



Somite. Podobranchi^e. . . Pleukobranchi/e. 



Anterior. Posterior. 



VII. . . . O(epj-) .. .... .... = 0(epr) 



VIII. ... 1 .... 1 .... .... = 2 



IX. ... 1 .... 1 .... 1 .... = 3 



X. ... 1 .... 1 .... 1 .... --=3 



XI. ... 1 .... 1 .... 1 .... 1 = 4 



XII. ... 1 .... 1 .... 1 .... 1 =4 



XIII. ... 1 .... 1 .... j- .... 1 = 3 + r 



XIV. ...0....0....0....1 =1 



6 + epr + 6 + 4 + r + 4 = 20+r + epr 



The epipod of the first maxillipeds bears about twenty gill filaments 

 on the upper half of its external face. The posterior arthrobranchia 



p. 771 ; TheCrayfish, p. 250, fig. 64, 1880.— Oktmann, Zoolog. Jahrb., Abth. f. Syst.,VI, 

 p. 9, 1891. Habitat. — Southern Brazil: Porto Alegre and near Eodersberg (von 

 Martens), Eio Grande do Sul, Sao Lourenzo (Ortmann). Types in Berlin Zoolog. 

 Mus., Nos. 3322, 3448 (von Martens). 



