CAMBARTJS. 3 



lack the bilobed plaited lamina of the Potamobiinas, although the stem may 

 be expanded into a wing ; the epipodite of the first maxilliped almost 

 always carries branchial filaments ; the coxopoditic setas terminate in hooks; 

 the telson is not divided by a transverse suture.* 



Six genera of Parastacinse have been described ; viz. Astacoidcs, by Gue- 

 rin ; Cheraps and Engcms, by Erichson ; Paranephrops, by White ; Astacopsis 

 and Parastaeus, by Huxley. Some of these genera are based on too trivial 

 characters to be valid. The group will be revised in the second part of this 



memoir. 



CAMBAEUS. 



In the genus Cambarus, established by Erichson in 1846, t the cephalo- 



thorax is subcylindrical. The last thoracic somite is devoid of gills, neither 



are there any traces of rudimentary pleurobranchiae on the anterior somites ; 



the hindmost podobranchia has no lamina. The branchial formula is as 



follows : — 



Somite, t Podobranchia. ArthrobrahchijE. Pleurobraxciii.k. 



Anterior. Posterior. 



VI (■■]..) . ... ... = 0(cp.) 



VII 1 ... 1 ... ... = 2 



VIII 1 ... 1 ... 1 ... = 3 



IX 1 ... 1 ... 1 ... = 3 



X 1 ... 1 ... 1 ... = 3 



XI 1 ... 1 ... 1 ... = 3 



XII 1 ... 1 ... 1 ... = 3 



Kill ... ... ... = 



6-fep. + 6 + 5 + = 17 + ep. 



This gives a total of thirty-four branchiae, counting those on both sides of 

 the thorax. The orifice of the green gland is situate near the apex of the 



* Chilton (Trans. New Zealand Inst., Vol. XV. pp. 152, 163, PI. sx. fig. 7, 1882) has observed that 

 the internal male reproductive organs in Paranephrops setosus are very different from those in the Potamo- 

 bihue. In the former the testes are two long tubes united by a transverse commissure, while in the latter 

 they form a trflobed organ through the coalescence of the right and left testes posterior to the vasa deferentia. 

 I have dissected an tindescribed Parastacine from Chili, and find the testes to agree with those of Para- 

 nephrops. It will probably be found that all the Parastacince agree in this regard. On account of the resem- 

 the internal mule generative organs in Paranephrops and Palinurus, and the further agreement of 

 the Parastacince and Palinuridce in the absence of the first pair of abdominal appendages and presence of 



I ked seta?, Chilton has forced these groups into too close relationship. Cf. T. JctTery Parker, in the same 



journal, Vol. XVI. p. 305. 



•|- Uebersichi der Lrten der Gattung Astacus. Arch. f. Natiirgesch., XII. Jahrg., Bd. I. p. 88. 



I The somite that bears the first pair of maxillipeds is here reckoned as the sixth. 



