CAMBARUS. 3 



lack the bilobed plaited lamina of the Potamobiina?, although the stem may 

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

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

 the telson is not divided by a transverse suture.* 



Six genera of Parastacinoe have been described ; viz. Axtacoidcs, by Gue- 

 rin ; Chiracs and Hue/ecus, by Erichson ; Paiwicphrops, by White ; Astacopsis 

 and Pamstacus, 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. 



CAMBARUS. 



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. J 1'oDonnAxcm.E. ARTHBOBEAKCHI^. PLEUROBRANCIII.E. 



Anterior. Posterior. 



. . . . . (cp.) 



. . . . . 2 



. . 1 . . . 3 



. . 1 . . . 3 



. . 1 . . . 3 



. . 1 . . . 3 



. . 1 . . . 3 



. . . . . 



6-j-ep. + G + 5 + = 17 + op. 



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

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



* Cliilton (Trans. New Zealand List., Vol. XV. pp. 152, 103, PI. xx. fig. 7, 1882) lias observed that 

 the internal male reproductive organs iu Pantiirjilirops selosus are very different from those in the Potamo- 

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

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

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

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

 blance of the internal male generative organs in Parancphrops and Palinurus, and the furl her agreement of 

 the Parastarina 1 and Palinuridte in the absence of the first pair of abdominal appendages and presence of 

 hooked setae, Chiltou has forced these groups into too close relationship. Cf. T. Jeffcry Parker, in the same 

 journal, Vol. XVI. p. 305. 



f Ucbcrsicht der Arten dcr Gattung Astacus. Arch. f. Xaturgesch., XII. Jahrg., Ed. I. p. S3. 



| The somite that bears the first pair of maxillipcds is here reckoned as the sixth. 



