106 STALK-EYED CRUSTACEA. 



the second antennae distinguishes Calastacus from Calocaris. The second 

 antenna of Calocaris macandreoi is represented on Plate XXVII., Fig. 2, 2", 

 for comparison with the same organ of Calastacus (Fig. 1''). 



Calastacus stilirostris Fax. 

 Plate XXVIL, Fig. 1-V. 



Bull. Mus. Comp. Zool. XXIV. 194, 1893. 



Male. — Carapace laterally compressed, naked, punctate ; rostrum long, 

 narrow, acute, apex slightly upturned ; two strong spines directed upward 

 and forward at the base of the rostrum ; from the root of the rostrum the 

 median dorsal line of the carapace is very convex ; a light median carina 

 runs along the back from the base of the rostrum, fading out before reach- 

 ing the hind border of the carapace. The gastric area is lightly corrugated 

 on each side of the carina. Abdomen longer than the carapace (including 

 the rostrum), naked, smooth ; first segment small, with rudimentary pleural 

 projections ; pleura3 of the succeeding segments broad, rounded, and bent 

 outward ; telson long, quadrangular, with convex hind border. 



Eyes rudimentary, subglobose, devoid of pigment and corneal facets. 

 Peduncle of first antenna composed of three stout segments, decreasing in 

 size successively from the first to the third. Basal segment of second an- 

 tenna provided with a sharp spine on inner edge of lower side ; second 

 segment armed with a long and sharp distal external spine (stylocerite) ; 

 from between the base of this spine and the following segment springs a 

 slender, sharp, articulated spine (scaphocerite) which nearly reaches the 

 end of the succeeding segment; inner edge of the second joint also carries 

 a median and a distal spinule, the latter of which is the larger ; the third 

 and fourth segments are unarmed, the latter short and carrying a long 

 flagellum, which exceeds the whole length of the body. Epistome largely 

 developed, terminating anteriorly in a triangular process at the base of the 

 antennules. 



Chelipeds long, symmetrical on the two sides ; coxa furnished with a 

 small spine on the anterior border of the distal end ; the ischium has from 

 one to four spines on the lower margin ; merus laterally compressed, armed 

 with a spine on the upper edge near the distal end, and a variable number 

 of .spines (four to eight) on the lower edge ; one of these, near the distal 

 end of the segment, is very long ; there is also a small spine on the ex- 



