CHAP. 111. THE EBURNIN^!. 81 



the aperture ; there is also no internal canal ; the inner 

 lip sometimes has a row of tubercles. The most typical 

 species, however, is the Polytropa crispata. * As we re- 

 cede from this genus, and approach to Plicatella, we 

 find the spire increasing in length ; the numerous 

 crisp undulations give place to small nodules and little 

 tubercles at the base of the inner lip, so that the two 

 genera became united : the circle of the Scolymince 

 is closed ; and this, without the deficiency of a single 

 link in the chain of connection which binds all the five 

 genera together. 



(71.) The next sub-family, Eburnince, is one of very 

 great interest, since it brings together certain genera 

 whose station has hitherto perplexed us all. For- 

 tunately, however, Mr. Gray has characterized the re- 

 markable little genus Cyllene ; and the possession of 

 other species, joined with those of Rhinedomus, before 

 alluded to, have prevented us falling into some errors : 

 the discovery of the basal sinus, also, on the outer lip of 

 Rhinedomus, at once opens a passage to Cyllene, which 

 still retains a costated and somewhat cancellated exterior, 

 with the basal sinus of the last genus. It deserves es- 

 pecial notice, that the species described by Mr. Gray 

 has a distinct channel round the suture, but the other 

 we possess has not. Now, this variation is precisely 

 what is met with in the genus Eburna, the types of 

 which are channeled, the others not. The slight striae 

 at the base of the pillar in Cyllene, are explained by 

 its analogy to Oliva, just as its obsolete notch typifies 

 its reference to Strombus. Other species will no doubt 

 soon come to light ; so that, with these facts before us, 

 we have no hesitation in placing Eburna as the next 

 type. Between this last, and Struthiolaria, there exists 

 the most intimate relationship in regard to their animals ; 

 both have a comparatively small foot, but a probosci- 

 diform mouth of excessive length, particularly that of 

 Struthiolaria, which, when fully protruded "\, is more 



* Chemnetz, 187. fig. 1802, 1803. Ency. Meth. pi. 419. fig. 2. 

 f See the animal of Struth. crenata, Voy. d' Astrolobe, pi. 31. figs. 8, 9. 

 6 



