FRKSinVATKR CRAYFISIIKS OK ALTSTItALlA. 105 



prolonged droughts, where all excejit the deepest water-holes 

 dry up, but presumably its burrowing habits save it. It seems 

 probable, from au examination of the anatomical features of the 

 land-Crayfishes of Victoria and Tasm;vni;i belonging to the genus 

 Engceus, that this latter genus has been derived from Chd'vaps 

 by an intensification of the burrowing habit and of the structures 

 associated with it. 



Genus Cu.ERArs. 

 (Erichson, Arch. f. Naturg. xii. 1846, p. 94.) 



Arthrobranch of last- leg but one somewhat reduced, but 

 without fleshy peduncle and consisting of fairly numerous small 

 filaments springing from a very short base. These filaments are 

 pointed at the end (PL XXVII. fig. 25), The ala on the podo- 

 branchs is broad as in Parac]iceraps. Many of the gill-filaments 

 attached to stem of podobranchs carry long curved hooks as in 

 Farachrrraps ; the filaments on the other gills are either round or 

 pointed, but do not carry hooks (fig. 26). 



The liook-setfB on coxopodites are sharply recurved. 



The antennal scale is not bi-oad as in ParacJuvraps, but lu'oadens 

 gradually after terminal spine (fig. 28). 



The lateral keels of the rostrum are usually very sharp and 

 conspicuous, but they may be absent (C. int&nivedlus). 



The lateral carina ou carapace is well marked, and may be very 

 sharp and pfominent, and there may also be a well-marked 

 median caiina. 



The distance between the tip of the rostrum and the cervical 

 suture is distinctly longer than that between the cei'vical suture 

 and the posterior border of caiapace. 



The steiiinl keel is shaip and very prominent (fig. 31). 



The int^rantennal spine ends in a sharp point (fig. 27). 



The great chela has the carpus either veiy long and slender, 

 and unprovided with a carpet of downy haii*(, or else provided 

 with hairs and stoutly built. 



In all other I'espects the generic charactei-s, e, g. of the niouth- 

 jiarts, tekon, and uropods, etc., agree exactly with Fcirachxeraps. 



Remarks on the above geuii^. — The diagnostic characters by 

 which Chcuraps may be distinguished from Pm^ich(»^raj%s aie 

 (1) the nature of the posterior aithrobranch, (2) the antennal 

 scale, (3) the distance between cervical suture to rostrum and 

 cervictl suture to posterior border of carapace, (4) the intei-antennal 

 spine, and (5) the sternal keel, 



Ch^RAPS QUINQUECAftlNATUS. (Pls. XXIII. tk XXVII. figS. 



25-29.) 

 The Gilgil 



(Gray, Eyre's Central Australia, vol. i. p. 410, pi. iii.) 

 The rostrum is modei-ately excavated, with lai^her prominent 



