CHAP. III. THE ORDER GASTEROPODA. 53 



So singularly do the Aptera represent the Dithyra 

 by the head (as in spiders and scorpions) being con- 

 founded with the trunk, that they might even, without 

 any violation of propriety, be termed acephalous in- 

 sects. But we presume enough has now been said on 

 this set of analogies, to satisfy the unprejudiced reader. 

 And having now sufficiently dwelt upon our arrange- 

 ment of the Testacea as a class, we may at once pro- 

 ceed to the details of the tribes in which the whole 

 are here arranged. 



CHAP. III. 



ON THE ORDER OF GASTEROPODA, ITS PRIMARY DIVISIONS, AND 

 THE CHARACTERS AND ANALOGIES OF THE MURICID-dE AND 

 THE TURBINELLID^E. 



(43.) THE gastropod shell-fish, as we have already 

 shown in the preceding pages, stand at the head of the 

 testaceous Mollusca, a station which both Cuvier and 

 Lamarck have also assigned to them. This has now been 

 confirmed by the theoretical and analogical tests with 

 which our last chapter was concluded. But as our ar- 

 rangement of these animals will be in many respects 

 very different from that of preceding writers, it will be 

 proper, before submitting its details to the reader, that 

 we should take a short review of the group as it at pre- 

 sent stands in existing systems. 



(44.) On referring to the definitions given in the 

 Regne Animal of the order Gasteropoda*, and to the 

 animals composing it, we find it embraces more than 

 nine tenths of the whole of the Mollusca inhabiting 

 univalve shells, and by far the greater part of such as 

 are naked. The inevitable consequence of thus includ- 

 ing a multitude of groups, differing from each other in 



* Griffith's Cuvier, xii. 21. 

 E 3 



