178 



SHELLS AND SHELL-FISH. 



PART I. 



distorted aspect of its mouthy — although quite unique 

 in this group, — are not its only characters; for at the 

 base of the aperture is a little emargination or notch, 

 analogous to what is seen in Helicina, Leucostoma, and 

 Anastoma. By the length of its spire, it evinces such 

 an affinity to Leptospb'a, that we insensibly find we have 

 returned to the group we commenced with. The sub- 

 genera of Biilimus thus form a circle, without the absence 

 of a single link in the chain of continuity. 



(167.) The sub-genera Bulimus and Auricula are 

 the only two which will require further illustration. 

 The first, from being pre-eminently typical, contains, 

 Vike Achatina, sectional types, representing the five prin- 

 cipal forms in this family. The Bulimus hcBmastomus 

 (Jig. '2,6.) is the chief of these, and is an exact counterpart 



of the Achatina ])erdijc Lam. of 

 the opposite circle. It is a 

 large ventricose shell, with a 

 spire much shorter than the 

 body-whorl, and of only four 

 volutions. In the next type, 

 Bulimus interruptus* of La- 

 marck, these proportions are 

 not preserved ; the form is 

 more slender, the body-whorl 

 less ventricose, the spire more 

 lengthened, and the whole aspect 

 reminds us of Achatina regi- 

 na t and its allies. These are followed by such shells as 

 Bui. /M7>;-icM.9 Lam., having very much the cylindrical form 

 of Pupa; the outer lip is nearly round, but there is no 

 inner lip, or any tooth in the pillar. In the third mo- 

 dification we see a complete prototype of the sub-genus 

 Goniostoma, in that singular shell the Bulimus Lyonc- 

 tianus, where the aperture protrudes on one side, and 

 appears distorted. Last of all comes those small Pa- 

 cific species (mistakingly separated as a genus, under 



Chemnitz, pi. 101. fig. 938, 939. 



+ Zool. 111. 1st Series. 



