2 A REVISION OF THE AST.U'IIU-:. 



appendages of male transformed into stvliform organs, or else absent ; 

 external branch of posterior pair of appendages divided by a transverse 

 suture; gills composed of a stem beset with numerous cylindrical filaments 

 (trichobranchiae), those borne on the proximal segments of tbe thoracic 

 appendages (podobranchiae) imperfectly, or not at all, separated into a 

 proper branchial and a lamellar portion; just in front of tbe base of tbe 

 podobranchiae a pencil of long, fine seta? (coxopoditic seta 1 ) arises from a 

 small papilla on the proximal segment of the legs. 



Huxley has shown, in his essay " On the Classification and the Distri- 

 bution of the Crayfisbes," * that tbe family Astacidae, as defined above, 

 naturally falls into two subordinate groups, to which I would assign the 

 value of subfamilies, viz. : — 



1. The Potamobiix-E, comprising the crayfishes of North America, 

 Europe, and Asia. In these the first abdominal somite in the male bears a 

 pair of styliform appendages ; t the podobranchiae borne on the second and 

 third maxillipeds and on the first three pairs of legs are furnished with a 

 broad bilobed plaited lamina; the epipodite of the first maxilliped is desti- 

 tute of branchial filaments; the coxopoditic setae are acute, not hooked, at 

 the end ; the telson is commonly divided more or less completely by a 

 transverse suture. 



The subfamily Potamobiinae includes two genera : — 



a. Cambarus, distinguished principally by the absence of gills on the last 

 thoracic somite and the absence of a bilobed lamina from the podobranchiae 

 of the penultimate pair of legs. (Page 3.) 



b. Aslacus, characterized chiefly by the presence of a pair of branchiae 

 on the wall of the last thoracic somite, and a folded lamina on the podo- 

 branchiae of the thoracic appendages from the second maxilliped to the 

 penultimate pair of legs inclusive. (Page 125.) 



2. The Paeast.u ix.e, comprising all the crayfishes of the Southern 

 hemisphere ; viz. those of South America, Madagascar. Australia, Tasma- 

 nia, New Zealand, and the Feejee Islands. % In this subfamily the first 

 abdominal somite is devoid of appendages in both sexes; the podobranchiae 



* Proc. Zoolog. Sur. London, 1878, pp. 7j2-7S8. 



f The first abdominal appendages .-ire rudimentary nr absent in the female. 



\ In the collection of the United Stales National Museum there is a specimen of an undescribed Pa- 

 rastacine from Colima, Mexico, collected bj .1 Xantus. This is tin- only representative of the Parastacinso 

 which lias been found imrili of the equator. According to Huxley, op. cit., p. 771, there are two specimens 

 of Paranephrop; from the Feejee tslands in the British Museum. Perhaps the locality labels of the Mexican 

 and I eejee pi cimi us an 



