10 ASTACID^E. 



nonymous with C, Blandingii Girard, and that from this species I am 



not able to separate Afossarum. But having seen only one female type, 

 the identity must be proved by further investigation. A BlandingU 

 Le Conte is identical with C. Lecontei Hagen, or perhaps with Harlan's 

 species. A. spicuUfer is without doubt a new and good species, but I 

 am not able to separate it decisively from the type A angustatus. A. 

 htimanus and advena are new species; A. mameitlatw is entirely unknown 

 to me. 



After these reductions, we find the number of different species in the 

 United States to be twenty, — fifteen given by Mr. Ch. Girard and five 

 by Dr. John Le Conte. 



1852. Professor James D. Dana, in his Synopsis Familiarum Crus- 

 taceorum, in the Proc. Acad. Phila., VI. 15, divided the old genus 

 Astacus into two genera, Astacoides (segmentum abdominis maris 

 primum appendicibus carens) and Astacus (segmentum abdominis 

 maris primum appendicibus instructum). With Astacoides are united 

 Engceus and Cheraps, with Astacus Cambarus. He describes (p. 20) 

 Astacus leiuusculus from the Columbia River "pedesquinti branchiae 

 parvas gerentes." In his celebrated work. United States Expl. Exped., 

 Crustacea, I. 522, he says : •• Among the distinctions subdividing the ge- 

 nus Astacus, that of the presence or absence of prehensile appendages 

 to the first abdominal segments in males, fitted for use in coition, 

 appears to be of the first importance. But the texture of the caudal 

 segment, whether calcareous or not to its tip, cannot be of much value 

 in classification, for it varies in the same species with age, and must 

 therefore be somewhat dependent on the size of the species. The 

 presence of a branchia to the posterior pair of legs may prove to be a 

 characteristic of importance, requiring a subdivision accordingly ; but 

 of this we doubt. In the American species without this branchia. which 

 the author has examined, the medial posterodorsal region of the carapax 

 is narrow linear, while in the European species and that from Oregon. 

 having the full number of branchia 1 . this region is quite broad. But we 

 cannot say how far this is generally true. For the reasons stated, we 

 accept of Astacoides as a distinct genus, separated from Astacus by the 

 absence of appendages from the first segment of the abdomen, and we 

 unite with it Cheraps and Engceus of Erichson. The occurrence of the 

 Engcei in holes in moist earth is not peculiar to that group, for the 

 same habit has been observed by Professor S. F. Baird in an American 

 species. Cheraps may perhaps lie retained as a subgenus under Asta- 

 coides, on account of the absence of the posterior branchia 1 ; and. on the 

 same ground, and no other of importance. Cambarus may be retained as 

 a subgenus under Astacus." For this reason the author has retained 

 Cambarus as a subgenus under Astacus, in his Synopsis, I. 523, and in 

 the revision and emendation, II. 1433. 



