2 A EEVISION OF THE ASTACID.E. 



appendages of male transformed into styliform 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 the thoracic 

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

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

 podobranchiae a pencil of long, fine setre (coxopoditic sette) 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 Crayfishes," that the family Astacida?, as defined above, 

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

 value of subfamilies, viz. : 



1. The POTAMOEIIN^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 podobranchise 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 sette are acute, not hooked, at 

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

 transverse suture. 



The subfamily Potamobiintc 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.) 



1. Abacus, 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- 

 branchiso of the thoracic appendages from the second maxilliped to the 

 penultimate pair of legs inclusive. (Page 125.) 



2. The PARASTACIN^E, comprising all the crayfishes of the Southern 

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

 nia, New Zealand, and the Fcejee Islands. J In this subfamily the first 

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



e Proc. Zoolog. Roe. Li.mloii, 1878, pp. 752-788. 



f The first abdominal appendages are rudimentary or nhscut in tlio female. 



J In t.lic collection of the United States National Museum there is a specimen of an undescribcd Pa- 

 rastacine I'mm Culima, Mexico, collected by J. Xantus. This is the only representative of the Parastaciiise 

 which h;is IH-CII found north of the equator. According to Huxley, op. cit., p. 771, there are two specimens 

 nl' l',iranr]ihri>]is from the Fcrjrc Islands in the British Museum. Perhaps the locality labels of the Mexican 

 and 1'Yrjcc specimens are erroneous. 



