CHAP. III. THE FUSING. 91 



also is marked by distinct longitudinal ribs, and has a 

 coronated row of little mucronate spines, much like 

 those of the harps : the type is the Fusus ficulneus, a 

 fossil of Grignon.* — 5. and lastly, we come to those large 

 species represented by Fusus colossus, coronatus, Moi'io, 

 &c., which we have arranged in the genus Hemifusus ; 

 they are, indeed, only half fusiform, as the spire is 

 shorter than the aperture : they are also distinguished 

 by an internal canal, and the whorls are coronated with 

 compressed spines : it is easy to perceive, by the very 

 aspect of these shells, that they form the passage to the 

 PurpuviB ; and their relation is so close, that, until we 

 know something of these animals, we feel somewhat 

 uncertain as to the station of such species as carnaria 

 and Cochlidium. Hemifusus, thus standing between 

 Strepsidura and Chrysostomus^ completes the circle of 

 the FusincB. 



(79-) Upon taking a general view of these shells, 

 we cannot but observe, notwithstanding all their modi- 

 fications, that the predominant characters of the group, 

 more or less, are preserved. In all of them we find 

 shells more or less — equally or unequally — fusiform ; 

 that is, their thickest part is in the middle, and their 

 two extremities attenuated to a point. No teeth, either 

 marginal or internal, are ever seen on the outer lip, 

 while the inner is invariably smooth : the spire, except in 

 one type, is always longer than the basal canal; whereas, 

 in the PyruHiKP, the very reverse of this takes place. 

 It has often been remarked by our leading zoologists,, 

 — and we have repeatedly illustrated the truth of the 

 position, — that no groups, whether generic or otherwise, 

 are so natural and so demonstrable as those which are 

 linked to others by mtervening gradations of form. 

 This is, indeed, completely opposed to the old opinion 

 formerly entertained, that no such divisions should be 

 tolerated in systems, but such as were distinctly separated 

 from each other; or, in other words, that, so soon as the 



* The Fusus heptagonus (Ency. M^th, pi. 428. fig. 7.) probably belongs 

 also to this genus, — although as an aberrant species. 



