36 
Mr. Toulmin Smith on the Classification 
IV. — On the Ventriculidse of the Chalk; their classification. 
By J. Toulmin Smith, Esq. 
[Continued from vol. xx. 1st Series, p. 191.] 
I HAVE thus described with some detail the structure which marks 
a large group of fossils from the chalk, and have further endea- 
voured to show what are the natural affinities of the group thus 
marked. The only clue has thus been obtained towards arran- 
ging, in a true and natural classification, those widely varied 
forms to which, under various secondary modifications, this 
structure belongs. The few of these which have hitherto been 
known have been uncharacterized except by names as various as 
the different writers, and which, being names merely, could leave 
no impression of reality on the mind of the inquirer. 
It will assist the inquirer, and will much enhance the import- 
ance of the present investigation, if, before entering on the de- 
scription of their modifications, something is said of the strati- 
graphical distribution of these fossils. 
From what has already been stated, it will be obvious that these 
fossils require to be sought : they can seldom fall in the collec- 
tors way as do fossils having solid parts, Testacea, Vertebrata, 
&c. If found at all in the hands of the dealer they will usually 
be fragmentary only, or in a matrix, the flint, the deceptive 
character of whose obvious appearances has been already shown. 
By far the greater part of the forms assumed are, besides, such that 
no blow of the hammer can disclose the character of the fossil. 
It is necessary to premise thus much that it may be under- 
stood that the fact of these fossils not having yet been recognized 
in particular localities or strata is no proof that they do not exist 
therein ; and, now that the true structure characteristic of them 
has been described, it may be hoped that the presence of some 
representatives of the family may be detected much more widely 
than has been hitherto suspected. A mere fragment may now 
serve for the detection of that presence*. 
As far as can be gathered from the various authorities already 
cited, it would appear that these fossils are more abundant in 
England than in any other country. In the chalk of Kent, 
Sussex, Norfolk, Wiltshire, and the respectively adjoining locali- 
ties, some of the forms are abundant, though in each region the 
localities in which they abound are certainly restricted. In the 
chalk of Yorkshire they appear to be much less abundant. In- 
deed many bodies which have heretofore been grouped as Ventri- 
culidce from that region have no relation to that family ; while 
* Of course not for the determination of species, or, necessarily, even of 
genus. 
