ASTACUS. 153 
groove on each side of the body) and in the shape of the anterior process of the epistoma, 
which is triangular with convex sides. It would seem to approach A. angulosus in the 
spiny character of the carapace. Schimkewitsch affirms that intermediate forms connect 
A. pachypus with A. leptodactylus (Government of Riazan), and A. leptodactylus with 
A. fluviatilis (Governments of Toola and Moscow). He evidently inclines, with Gerst- 
feldt, to the opinion that all the Eurasiatiec Astaci, excepting those of the Amoor basin 
and Japan, form but two distinct species, viz. A. nobilis (including the varieties A. flu- 
viatilis, leptodactylus, angulosus, pachypus, Colchicus, etc.) and A. torrentivm (including 
A. pallipes) of Western Europe. In the material that has fallen into my hands I 
have not seen indications of the intermediate forms, and I have been led to consider all 
the forms just named to be valid species, with the exception of A. angulosus. 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 pachypus, RatHKE, Mém. Acad. Impér. Sci. St. Pétersbourg, I]. 365, 1837. (Separate, 1836.) 
Astacus Caspius, Fxcuwawp, Bull. Soc. Impér. Nat. Moscou, 1838, p. 149. — Fauna Caspio-Caueasia, p. 181, 
Tab. XXXVI. fig. 2, 1841. 
Astacus pachypus, Bricuson, Arch. Naturgesch., XII. Jahrg., I. 91, 1846. (After Rathke.) 
Astacus Caspius, PRICHSON, op. cit., p. 92, 1846. (After Hichwald.) 
Astacus fluviatilis, var. pachypus et Caspius, GerstrELpt, Mém. Acad. Impér. Sci. St. Pétersbourg, IX. 566, 
584, 1859. 
Astacus pachypus, HeiiER, Die Crustaceen des siidlichen Europa, p. 217, 1863. 
Astacus pachypus, Kesstrn, Bull. Soc. Impér. Nat. Moscou, XLVIII. 254 [854], 1874. 
Astacus pachypus, 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. 
ll. Astacus Colchicus. 
Astacus Colchicus, Kesstrr, Bull. Soc. Impér. Nat. Moscou, i. 2, 1876. 
Astacus Colchicus, Faxon, Proc. Amer. Acad. Arts and Sci., XX. 158, 1884. 
Distribution. — Upper part of Rion River and tributaries, Transcaucasia. 
According to Kessler, Astaci are found in Lake Palostom, south of the 
mouth 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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