REPORT ON THE CRUSTACEA MACRURA. 195 



According to Rcesel and Huxley the young- in Astacus arc attached b)^ means of the 

 first pair of pereiopoda, hut according to Mr. Wood-Mason, 1 in the New Zealand species 

 of Paranephrops the young are attached by the strong hooked claws of the two hinder- 

 most pairs of feet to the swimmerets beneath the pleon. 



Astacopsis, Huxley. 

 Astacqpsis, Huxley, Proe. Zool. Soc. Loud., 1878, p. 764. 



This genus resembles Astacoides of Guerin 2 externally, but differs in having a 

 second joint to the outer branch of the first pair of siagnopoda, in having a larger 

 median ramus, and a longer second joint to the outer branch of the third pair of siagno- 

 poda ; in having a basecphysis that reaches to the extremity of the dactylos in the 

 first pair of gnathopoda ; in having a two-jointed basecphysis that reaches to the 

 extremity of the ischium in the second pair of gnathopoda, and in having on each side 

 four well-developed pleurobranchiaj, eleven arthrobranchiae, besides six podobranchise, and 

 four movable plates, one of which is attached to the podarthrodial membrane of each of 

 the pereiopoda except the posterior pair. 



In Astacopsis there are four pleurobranchias, eleven arthrobranchias, and six podo- 

 branchiae, while in Astacoides there are, besides the six podobranchise that are common 

 to all the genera of the Astacidse, ten arthrobranchise, five of which are rudimentary, 

 and one pleurobranehise. Moreover, the basecphysis of the second pair of gnathopoda 

 is unbranehed, and approximating to a rudimentary condition, and that of the first 

 pair is shorter than the limb to which it is attached. The second or terminal joint 

 of the outer branch of the third siagnopoda is short and in a rudimentary condition, 

 and the outer branch of the first siagnopoda has no second joint. The metabranchial 

 plate attached to the fourth pair of pereiopoda is rudimentary instead of being large as 

 in Astacopsis. 



Geographical Distribution. — Specimens of this genus have been taken in several of 

 the rivers of the southern divisions of the Australian continent, whereas Astacoides is 

 confined to Madagascar. 



~&~ 



Astacopsis spinifer (Heller) (PI. XX VIII.). 



Astacoides spinifer, Heller, "Novara" Reise, Crustaceen, p. 102, tab. ix., 1865. 

 Astacus armatus, von Martens, Ann. and Mag. Nat. Hist., ser. 3, vol. xvii. p. 359, 1866. 

 Australian Crayfish, unnamed, Huxley, The Crayfish, p. 307, fig. 76. 

 Australian Crayfish, J. E. Gray, Eyre's Journ., Exped. Cent. Aust, vol. i. p. 407. 



Rostrum sharp pointed and armed on either side with three sharp teeth near the 

 anterior extremity. Dorsal surface of the carapace smooth and divided by a deep 



1 Ann. and Mag. Nat. Hist., ser. 4, vol. xviii. p. 307. 2 Revue Zoologiquc, vol. ii. p. 109. 



