105 



prevails. Numberless illustrations of design and adaptation 

 have forced themselves upon attention in the course of the inves- 

 tigation, and more might have been suggested had it not been 

 feared that the allusion would appear obtrusive. 



It cannot be supposed that the forms which have been here 

 described constitute all that existed of this family even in the 

 cretaceous seas. In my own collection are a few individuals as 

 to whose specific identity I have some doubt, but as to which I 

 would wait for further means of observation rather than rashly 

 increase the number of species. Doubtless, now that the struc- 

 ture has been described, and figures and descriptions of such 

 numerous forms been given, some attention will be directed to 

 the subject and other forms be found. From the great extent of 

 the materials on which these observations have been made, it 

 may, however, without presumption, be conceived that the prin- 

 cipal typical forms are here included, and that any which may 

 hereafter be clearly ascertained will range themselves easily in 

 one or other of the groups whose characters, general and special, 

 have been here determined. 



Many other obscure fossils are found in the chalk, either gene- 

 rally unknown or distinguished by names which impart little idea 

 of vitality to the objects to which they have been attached, a 

 vitality which it is sought in vain to realize by any descriptions 

 which have hitherto been published. To a more particular ex- 

 amination of some of these, the attention of such readers as have 

 followed with any interest the present inquiry into the structure, 

 affinities and forms of the Ventriculidse, may, at a future day, be 

 perhaps invited. 



