130 ashford: note on BULIMUS heterostomus. 



whorls of which it is formed are rounded, separated by a deep 

 suture, and ornamented with fine, transverse, raised lines, which 

 are numerous, regular and very oblique; the aperture is roundly- 

 ovate, apparently thickened within, and with the margin slightly 

 reflected, . . ." and he ends by remarking "apparently it is 

 very rare." I offer a few remarks on this description. 



Among the four examples of B. heterostomus which I have 

 found in this neighbourhood, there is no instance of decollation 

 of the apex. One is immature and therefore not likely to be so 

 affected, but the other three are either almost or completely of 

 full growth. From this it may be inferred that the defect was 

 exceptional, and that the geologist has as good a chance of 

 meeting with a complete spire as with one that has shed its early 

 whorls. Spiral shells occurring in the limestone at Sconce are 

 very frequently found with the upper or early whorls in an empty 

 slate into which moisture charged with lime-carbonate has per- 

 colated, forming incrustations of crystals. In extracting the fossil 

 this brittle structure at the apex comes away in fragments or as 

 frequently flies away unseen when the rock is splintered and an 

 apparently decollated specimen only is secured, but the complete 

 form may be observed in the matrix. I do not suppose for one 

 moment that the author of Eoc. Moll, was deceived by this 

 appearance, though a less careful observer might easily be led 

 into error. His figure of the matrix seems not to show the apex 

 of the shell but to suggest a true case of decollation My own 

 specimens were obtained from a different locality, viz. : — the 

 uplands of Thorley, where the embedded organic remains are 

 generally found filled to the very apex, and where it is not 

 uncommon to meet ^vith examples of Helix, Pla^iorbis, LimncBa, 

 &c., with the shell preserved though in a white and very friable 

 condition. 



The whorls are eight in number, gradually increasing in size, 



