178 SHELLS AND SHELL-FISH. PART I. 



distorted aspect of its mouth, 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 Leptospira, that we insensibly find we have 

 returned to the group we commenced with. The sub- 

 genera of Bulimus 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, 

 like Achatina, sectional types, representing the five prin- 

 cipal forms in this family. The Bulimus htemastomus 

 (fig. 26.) is the chief of these, and is an exact counterpart 

 of the Achatina perdix 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 bodyrwhorl 

 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 

 BuL lubricus 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 Lyone- 

 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. t Zool. 111. 1st Series. 



