2 MIOCENE FAUNA. 



dichiantij Fer.) the shells of which lie by millions buried in the 

 sands of Caniyal in Madeira and in Porto Santo. On the spit 

 of Caniyal, Prof. Heer saw a piece of ground completely covered 

 with the shells of this species (associated with those of several 

 others), so that numbers of them were crushed at every step. 

 Here and there, however, they are imbedded in the sand, and 

 thus protected. They have evidently been brought together 

 during a long period of time into a small lake-basin, and enve- 

 loped in sand and mud; but they have perfectly preserved their 

 form, as they were exposed to no pressure. In the same way 

 probably have been produced the accumulations of snail-shells 

 which we not unfrequently meet with in the Swiss Miocene 

 marls, as at the Paudeze, at Delsberg, near Schwamendingen, at 

 Frauenfeld, &c. ; but in these places the shells are generally so 

 crushed by the pressure of the overlying masses of rock that 

 they can rarely be determined. 



Helix inflexa. Mart., which occurs near Delsberg, like H. 

 Ramondi, is nearly allied to a species inhabiting the Atlantic 

 islands (H. portosantana, Sow.) ; while Helix sylvestrina, Ziet. 

 (fig. 202), the commonest species of the Swiss Molasse, and the 

 allied species H. moguntina, Desh., which is also of frequent oc- 

 currence, represent European forms (H. sylvatica and splendida, 

 Drap.). The former is so well preserved at Vermes (in the 

 Delsberg) that we can still recognize dark bands (three to five 

 in number) which ornamented the shells. In Helix rugulosa, 

 Mart., which is very plentiful in the valley of Delsberg, four 

 coloured bands may still be seen on the shell. This species 

 finds its nearest allies (H. elevata, Say, and H. pennsylvanica, 

 Green) in the West Indies and North America. Helix ehingen- 

 sis, Kl. (from Delsberg), and H. osculum, Th., most nearly ap- 

 proach a species from Texas (H. Berlanderiana, Mor.), whilst the 

 great Helix insignis, Schubl., which has also been found abun- 

 dantly in the valley of Delsberg, must be characterized as a 

 West- African form (allied to H. rosacea, Mull.) . 



The Helices are frequent in the Swiss Miocene, appearing 

 almost in all places where plants occur. Eleven species are 

 found in the marine Molasse ; these have been carried by run- 

 ning water into the sea, and have thus mingled with its inhabi- 

 tants. The Pupa and Clausilice arc much less common ; but 



