Zoology.-] NATURAL HISTORY OF VICTORIA. ^Crustacea. 



Plate 29. 



ASTACOIDES BICARINATUS (Gray sp.). 

 The Yabber Crayfish. 



[Genua ASTACOIDES (Guer.)- (Sub-kingd. Articulata. Class Crustacea. Order 

 Decapoda. Sectiou Maenira. Fam. Astacidas.) 



Gen. Char. — General form and character of Astacus, but with the first segment of the 

 abdomen destitute of appendices. Abdominal feet membranous, with a row of small calcareous 

 plates on each margin. Outer pair of tail-fins jointed, with the distal portion thinner and less 

 calcareous than tlie proximal one ; inner lobe not distinctly jointed, and calcareous to the end. 

 Fresh waters of Madagascar and Australia]. 



Description. — Beak acutely pointed, bounded by a narrow, rounded, prominent, 

 smooth ridg-e on each side, between which the surfoce is nearly flat, slightly convex 

 behind ; apex acutely pointed, with a small tooth on each side, reaching as far 

 forward as the base of the last large joint of the outer antennae, or slightly behind 

 the base of the last large joint of the inner antennae, and behind the apex of the large 

 basal scale of outer antennte. Carapace subcylindrical, moderately convex above 

 and on the sides ; two long, narrow, prominent, subparallel ridges extend from the 

 orbits (one on each side), a little outside the base of the rostral marginal ridges, about 

 two-thirds o( the way to the nuchal furrow ; whole surface of carapace and abdomen 

 destitute of spines or tubercles, but impressed with moderately close, irregular 

 punctures ; outer pair of tail-fins with a distinct transverse joint at about two-fifths 

 from the base, separating abruptly the spinulose, serrated, posterior margin of the 

 thick, calcareous, proximal portions from the distal, thin, flexible, semimembranous 

 part ; calcareous basal portion of inner pair of fins nearly as long as the membranous 

 part, without joint or serrated division, but having a sharp spine terminating a ridge 

 along the outer edge and another terminating a larger ridge a little on the inner 

 side of the middle ; middle flap of the fin with the calcareous portion slightly 

 longer than the thin membranous portion, and having a small spine terminating the 

 lateral margin on each side. Anterior pair of feet or claws nearly equal ; the outer 

 edge, and under and upper surfaces of each hand moderately convex and smooth, 

 without spines, the inner edge compressed with a row of about 14 small compressed 

 blunt spines; the fixed and movable finger of each claw round and smooth on the 

 outer edge, with short incurved points, and having the inner edges set with very small, 

 numerous, unequal teeth ; carpus smooth above and outside, having one strong spine 

 in middle of inner edge, with one smaller below and in front of it, and one still 

 smaller at base with a few intermediate granules ; the next joint of the leg has a 

 compressed slightly -toothed or serrated upper edge (about six scarcely formed or 

 raised teeth), a smooth outer and inner surface with a small spine on each side of 

 carpal joint ; lower edge with two rows of very irregular small spinous tubercles. 

 Anterior median process of epistome semicircularly rounded, or very slightly pointed 

 and semielliptical, slightly longer than wide. Color: whole body and abdomen 

 dull pale-olive, varying in some to greenish-horn color; membranous part of tail- 

 flaps pale-brown ; anterior pair of legs bright-blue, the basal and outer portion of 

 upper surface of hand mottled with scale-shaped spots of dull ochreous-yellow, skin 

 of joints bright-red. Length of small average specimen from snout to tip of tail, 

 ■t inches 7 fines ; length of carapace from tip of snout along mid-line of back, 2 



[43] 



