90 



\ 



LXV. Sigaretus. A depressed oval, nearly auriform shell, with a 

 short spiral columella : the opening entire, very wide, spread out towards 

 the summit of the right lip, and longer than wide. 



The shell, for the reception of which Lamarck formed this genus, is 

 the Venus's ear ; Sigaretus, of Adanson ; Helix haliotidea, of Linnaeus ; 

 and Eulla velutina, of Muller. This is an exceedingly rare fossil. The 

 only specimen which I have seen is one which I obtained at the sale of 

 the Museum of Mr. Strange ; and which, I afterwards discovered, by 

 the purchase of some of Mr. Strange's manuscripts, had been thought of 

 sufficient consequence to be the subject of a plate engraved by Antonio 

 Gregori, from a drawing of Gaspero Massini. This is a Tuscan fossil. 



A fossil shell of this genus, but apparently not of this species, is found 

 in St. Peter's Mountain, Maestricht, and is figured by Faujas St. Fond, 

 Hist. Nat. de la Montagne de St. Pierre, P. 166, PL xxvm. Fig. 3. 



Plate VI. Fig. 9, is a magnified representation of a shell of this 

 genus, which is shown of its natural size, Fig. 10. This microscopic 

 fossil was found in the calcareous sand contained in the cavity of a 

 gigantic cerithites. 



LXVI. Argonauta. A very thin involuted boat-like univalve; the 

 spire turning into the opening ; with a double, tubercular keel. 



I have no knowledge of any shells of this genus having been found in 

 a mineralized state. 



