152 A REVISION OF THE ASTACID^. 



sources of the Ural River are not remote from those of the Ui, it is possible 

 that a spontaneous migration from the former into the latter has taken place.* 



Eichwald describes and figures A. leptodac/ytu-s, var. Gasjm, from the Cas- 

 pian Sea near Lenkoran, as smaller than the normal form, the carapace 

 smoother, and the margins of the rostrum nearly smooth. It is probably 

 an immature stage of A. leptodactyliis. 



In Astacm angulosus Rathke, from the Crimea and adjacent region, the fin- 

 gers of the male are not elongated, as in Astacus leptodaetylus Eschscholtz, so 

 that the hand has much the same form as in the female of the latter species. 

 The rostrum, moreover, is broader, with its margins more nearly parallel 

 from the base to the lateral spines, and with its median carina prominent 

 and toothed toward the apex ; the abdominal pleura are shorter and broader 

 than in A. Iqitoilidijlus. The flattening of the sides of the carapace, by 

 which an angle is formed by the dorsal and lateral faces, is not characteristic 

 of this form, although it suggested the name to Rathke. The same condi- 

 tion is sometimes found in specimens that in all other respects agree with 

 the form leptodictylus, while in some examples of A. angulosus the branchial 

 regions are as convex as in A. Icptodactijlm. In the shape of the rostrum and 

 abdominal pleura A. angulosns approaches A.flumatilis, but it cannot be con- 

 fused with that species, on account of the shape of the chela, the double pair 

 of post-orbital spines, etc. Forms intermediate between A. angulosus and 

 A. leptodactylus, having the rostrum of the latter combined with characters 

 belonging to the former, are met with in the Sulak River, which flows into 

 the Caspian south of the Terek on the northern side of Mount Caucasus 

 (Gerstfeldt). It seems natural, therefore, to consider A. angulosus a variety 

 of A. leptodactylus. 



Since this account of the European Astaci was written, Wladiurir Schimkewitsclif 

 has published an insufficient preliminary notice of an Astacus from the neighborhood of 

 the town of Turkestan in the valley of the Jaxartes. It is closely related to A.fluriatllis 

 and A. leptodactylus, perhaps not specifically distinct from one of these. It seems to be 

 subject to considerable variation in the form of the rostrum and telson. According to 

 Schimkewitsch it differs from all the allied species in the great development of spiny 

 tubercles on the sides of the carapace (there being four on the hind border of the cervical 



* With reference to the presence of A. leptodacti/lii* iu Western Siberia, see Kessler, op. cif., p. 371, 

 Middendorff, op. cit., p. SS5, and especially Koppen, " Notiz iiber die Ruckwauderung der Dreissena poly- 

 morphit Pall. Nebst einem Anhange : Ueber kiinstliche Verpflauzimg der Flusskrebse iu Russland." Beitr. 

 zur Kenntniss des Russischen Reiches, 2te Folge, Bd. VI., 1S83. 



f Der turkestanische Flusskrebs. (VorlauQge Mittheiluug.) Von Wladimir Schimkewitsch. Zoolo- 

 gischer Anzeiger, VII. 339-341, 23 Juni, 1884. 



