-CHAP. V. GENERA OF THE CONIN^E. 149 



and the next begins.* Such only are natural and per- 

 fect groups : they are the delight of the philosophic 

 naturalist, and the torment of the mere nomenclator. As 

 Conus is the most numerous in species, so it is the most 

 perfect in these gradation s, by which its five sub-genera 

 are blended into one circle. The superior heaviness 

 which belongs to the two typical divisions in each, is 

 very singidar, and may, probably, be owing to the 

 internal volutions of their shells not being so much ab- 

 sorbed as in the other types : a simple section, however, 

 will, no doubt, explain the cause. 



(138.) Whether Conus dormitor, and other fossil 

 species, really constitute the analogous genus in this 

 circle to the Pkurotomce, cannot be determined, as no 

 recent species, that we know of, have been discovered : 

 we shall, however, regard them in this light under the 

 generic name of Conorbis. The only remaining genus 

 is that of Conella, hitherto overlooked among the di- 

 versified shells placed in Columbella by Lamarck, where 

 they continue to the present day. They are all very 

 small, and perfectly resemble Cones in their shape ; but 

 they may be easily known by the outer lip, which ad- 

 vances upwards on the spire, and is marked internally 

 by distinct elevated striae. This is a most interesting 

 group ; for it not only connects this and the succeeding 

 sub-family of Columhellincn in the most satisfactory 

 manner, but, at the same time, it preserves an affinity, 

 on the other hand, to Conorbis. 



(139.) The Conine, thus arranged, form themselves 

 into the five following genera, analogous to the primary 

 divisions of the Strombidcje. The genus Conella (Jig. 17.«.) 

 connects this and the last sub-family. 



* There is one rule, however, which we have found quite sufficient for 

 this purpose. If, of three cliaracters of a given type, a species iwssesses 

 only one, and that but slightly developed, the probability is, that it really 

 belongs to the neiLt type ; or the question may be decided by the law of re. 

 presentation. Every natural and perfect group, of whatsoever value, con- 

 tains representations of all the other four groups of its own value in that 

 circle which unites them all. Thus, it will not be difficult for the natural- 

 ist to discover, in that sub-genus which includes Conus slriatus, represent- 

 ations (among the species) of all the other four. 



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