10 GEOLOGICAL MEMOIES. 



lata, and C. elongata are still tenants of the Adriatic and Mediter- 

 ranean coasts ; the others are of a Senegalian type ; and one of 

 them, G. crassicosta, Lam., is still living in this region, 



Astarte, 1 species, A. triangularis, Mont. This genus, which 

 begins with the Mountain Limestone, occurs frequently in cer- 

 tain Jurassic strata, and also existed during the Cretaceous period, 

 is completel)^ wanting in the Eocene deposits, those of North America 

 excepted. It is represented, however, but feebly, in the Neogene 

 strata. Its species are of frequent occurrence in the Oligocene 

 of Belgium, Central and North Germany, in the Neogene beds of 

 Liineburg, Sylt, North Sleswick, &c., and, most strikingly, together 

 with many recent species, in the English and Belgian Crags, prov- 

 ing thus a former connexion of the Crag Sea with the North At- 

 lantic, the present habitat of nearly all the living species. 



Unio, 9 species, all in the Congerian (Neogene freshwater) strata, 

 and mostly of decided North-American type. 



Nucwla Mayeri, Horn., N. nucleus, Lam., mostly in the sands, 

 the latter species occurring in almost all Eui'opean seas. 



Nucinella ovalis, Wood, identical with the form from the Crag. 

 Leda, 7 species, in the marls and plastic clays of the Leitha- 

 kalk. 



Lhnopsis anomala, Eieh., is of frequent occurrence in the same 

 localities as Leda, and also in the Lower Plastic Clay of Baden, &c. 



Pectunculus, 3 species, P. Fichteli, Desh., is extremely frequent 

 in the coarse sands of Leobersdorf (basin of Vienna), as also in 

 those of Korod (Transylvania). P. pilosns, Linn., occurs as fre- 

 quently in the Marls of the Leithakalk as in the existing Adriatic 

 and Mediterranean fauna, but is very scarce in the " Lower Plastic 

 Clays" ; P. obtvsatus, Partsch, seems scarcely to have extended 

 beyond the Vienna basin. 



Area, 15'species, among them are A. umbonata, Lam., A. Breis- 

 lacH, Bast., A. Tichteli, Desh., A. cardliformis. Bast., and 4. Turo- 

 nica, Duj., found in an arenaceous deposit of comparatively most 

 ancient date ; A. Noce, Linn., A. harhata, Linn., A. clathrata, Dfr., 

 and A. lactea, Linn., belong to the existing Adriatic and Mediter- 

 ranean fauna ; A. Hungarica, A. Rollei, A. dicliotoma, and A. 

 Pisum are new forms. 



General Results. Relative Age of the Strata in the Vienna Basin. — 

 The lowest strata in this basin are not those of most ancient date, 

 which are really represented by the sand-deposits around Korn 

 (north of the Danube), containing Cardium cingulatum, Goldf., and 

 other shells not to be distinguished from those of the Oligocene 

 fauna. Next to them come the sand-deposits of Grusbach, Grund, 

 Ebersdorf, Weinsteig, Poetzteiusdorf, itc, with a fauna perfectly 

 identical to those of the Swiss Molasse, the beds of Bourdeaux, Dax, 

 Perpignan,ikc.,and — as a contemporaneous formation — the calcareous 

 reef-deposits (Leithakalk, or NuUipore Limestone), frequent along 

 the coast of the old Tertiary sea, Steinabrunn, Nikolsburg, Gainfahrn, 

 Nussdorf, Grinzing, &c., their subordinate beds of marls including 

 plenty of shells, denoting a fauna remarkably analogous to the fauna 



