ASTACUS. 153 



groove on each side of the body) and iu the shape of the anterior process of the epistoma, 

 which is triangular with convex sides. It would seem to approach A. angulosus in the 

 spiuy character of the cai'apace. Schimkewitscli affirms that intermediate forms connect 

 A. pachypus with A. kptodadylus (Government of Eiazan), and A. leptodactylus with 

 A. fldiviatiiis (Governments of Toola and Moscow). He evidently inclines, with Gerst- 

 feldt, to tlie opinion tliat all the Eurasiatic Astaci, excepting those of the Amoor basin 

 and Japan, form but two distinct species, viz. A. nobilis (including the varieties A. flu- 

 viatilis, leptodactylus, anyulosus, jMchypus, Colchicus, etc.) and A. torrcntiuin (including 

 A. jiallipcs) of Western Europe. In the material that has fallen into my hands I 

 have not seen indications of tlie intermediate forms, and I have been led to consider all 

 the forms just named to be valid species, with the exception of ^. angidosus. Kessler, 

 who had unrivalled opportunities for forming a just opinion on this point, came to the 

 same conclusion. After all, to any one who believes that all these forms are descended 

 from a common ancestor, the question whether they constitute two species with marked 

 varieties, or whether they rather form two groups of closely allied species, is merely a 

 question of terms. 



10. Astacus pachypus. 



Astacus pachi/piis, Rathke, Mem. Acad. Iraper. Sci. St. Ptitersbourg, III. 365, 1837. (Separate, 1836.) 

 Astacus Caspiiis, Eichwald, Bull Soo. Imper. Nat. Moscou, 1838, p. 149. — Fauna Caspio-Caucasia, p. 181, 



Tab. XXXVl. fig. 2, 1841. 

 Astacus pachypus, Ericuson, Arch. Naturgescli., XII. Jahrg., I. 91, 1816. (After Ratlike.) 

 Astacus Caspius, Ericuson, op. oil., p. 92, 1846. (After Eichwald.) 

 Astacus fluciutilis, var. pachi/pits el Caspius, Gekstfeldt, Mem. Acad. Irajier. Sci. St. Petersbourg, IX. 506, 



584, 1859. 

 Astacus pacii/pus, Hellee, Die Crustacean des siidlichen Europa, p. 217, 1863. 

 Astacus pachypus, Kesslek, BuU. Soc. Imp6r. Nat. Moscou, XLVIII. 254 [354], 1874. 

 Astacus pachi/pus, Faxon, Proc. Amer. Acad. Arts and Sci., XX. 158, 1884. 



Distribution. — Brackish waters of the Caspian Sea and estuaries of rivers 

 flowing into the Caspian and Black Seas. Estuary of the Dniester at Kolo- 

 glea (Kessler) ; of the Boug at Nicolaiev (Rathke, Kessler) ; mouths of the 

 Volga, Astrakhan (Kessler) ; Lesser Oozen River ; Caspian Sea at Manghish- 

 lak (Kessler), Krasnovodsk (Kessler), and Bakoo. 



11. Astacus Colchicus. 



Astacus Colchicus, Kessler, Bull. Soc. Imp^r. Nat. Moscou, L. 2, 1876. 

 Astacus Colchicus, Fa,xon, Proc. Amer. Acad. Arts and Sci., XX. 158, 1884. 



Distribidion. — Upper part of Rion River and tributaries, Transcaucasia. 

 According to Kessler, Astaci are found in Lake Pala?ostom, south of the 

 nioutli of the Rion ; but whether they be A. Colchicus or not is unknown. 

 A. Colchicus is brought to the market of Tiflis from the upper Rion. It has 



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