ASTACUS. 129 



Somite. PoiJoiiRAxcin.K. Arthrobranchi.k. pLKi'iiOBUANtui.E. 



Auterior. J*osteriur. 



VI (op.) * . ... 



vn 



VIII 



IX. 



X 



XI 



XII 



XIII 



G -I- ep. + G + 5 + 1 4- 3 r = 18 -j- 3 )• + ep. 



The structure of the gills and coxopoditic sette is the same as in the 

 Astaci proper. 



2. Astaciis (Cambaroides) Dauricus. 



Plate X. figrs. 9, 9' (first abdominal appendages of male). 



Astacus Dauuricus, Pallas, Spicilegia Zoologica, Fasc. IX. p. 81, 1772. 



Cancer Dauuricus, Pallas, 1. c. 



Dauurische Krebs, Herbst, Versuch Naturgesch. Krabben u. Krebse, II. 42, 1796. (After Pallas.) 



Astacus leptorrhinus, Fischer, Bull. Soc. Imper. Nat. Moscou, IX. 467, Tab. V. fig. 1, 1S36. 



Astacus Dauricus, Eliicusos, Avcli. Natuvgesch., XII. Jahrg,, I. 94, 1846. 

 V; Astacus Da\uricus, Gebstfeldt, Mom. Acad. Imper. Sci. St. Petersbourg, VIII. 292, 1S59. 



 Astacus Dauricus, Kes.slek, Bull. Soc. Imper. Nat. Moscou, XLYIII. 301, 1874- 



Astacus {Cambaroides) Dauricus, F.wox, Proc. Amer. Acad. Arts and Sci., XX. 151, 1884. 



Habitat . — Upper portion of the Amoor River basin as far down as Alba- 

 sin, including the rivers Ingoda, Argoon, Onon, Shilka, and Nercha. It is 

 not found in the Gasinioor, a tributary of the Argoon (Gerstfeldt, Kessler). 



3. Astacus (Cambaroides) Schrenckii. 



Plate yn. fig. 3. 



Astacus Schrenckii, Kessler, Bull. See. Imper. Nat. ^Moscou, XL VIII. 363, 1874. 

 Astacus {Cambaroiih's) Sclireuckii, Faxon, Proc. Amor. Acad. Arts and Sci., XX. 151, 1884. 



Hahitat. — Lower part of the basin of the Amoor River (Kessler). 



In the form of the rostrum and in the possession of a lateral thoracic 

 spine, A. Schrenckii bears less resemblance to A. Dauricus, from the upper 

 part of the same river basin, than A. Japonicus does. On the other hand, 

 the cheliB and abdominal pleura of A. Schrenckii are very much like those 

 of A. Dauricus, while in A. Jajmiicus the cheliB are much shorter and broader, 

 the abdominal pleura broader and more rounded, than in the Amoorland 

 species. 



* The cpipodite of Ibe first inaxiUiped bears no branchial filaments. 



