42 



the forms hitherto collected there of true Ventriculidte are very 

 rare, if we may judge from the specimens in the museum of the 

 Yorkshire Philosophical Institution, for the opportunity of care- 

 fully inspecting which specimens I am indebted to the courtesy 

 of Mr. Charlesworth*. In England these fossils have not hitherto 

 been recognized in any other than the Cretaceous group. It is 

 probable that careful search will reveal them throughout all the 

 members of that group. At present they have been found in 

 five divisions of it ; viz. the Upper Chalk, the Middle Chalk, the 

 Lower Chalk, the Chalk Marl, and the Upper Greensand. The 

 prevalence indeed of certain forms is characteristic of certain of 

 these divisions f ; a result which unexpectedly displayed itself 

 after the classification presently to be exhibited had been worked 

 out from a cautious study of the individuals, and the value of 

 which result must therefore strike every inquirer. The particular 

 divisions characterized by the predominance of one or the other 

 class of forms will be shown in severally describing those forms. 



There is no a priori reason why representatives of these forms 

 should not be found in older and in newer formations than these 

 cretaceous beds. Still the fact of their not having been thus found 

 in England, where, in those cretaceous beds, some of them so much 

 abound, leads to some hesitation in relying implicitly on the 

 alleged much lower stratigraphical position of some foreign forms. 

 The foreign forms from the true chalk appear to be few r and rare ; 

 but there are several figures in Goldfuss, to some of which I have 

 already alluded J, probably representing forms belonging to this 

 family, which are there given as from the " Jurakalk." In the 



* In addition to the acknowledgements which I have already made, I 

 have the further pleasure of now recording the kindness, in affording me 

 the means of examining different specimens from very various localities, of 

 Mr. Lyell, Mr. Wetherell and Mr. Oakeshott of Highgate, Mr. Cunnington 

 of Devizes, Mr. Catt of Brighton, and Mr. Whittle of St. John's College, 

 Cambridge, besides that of Mr. Charlesworth as above-mentioned. I must 

 also acknowledge the kind assistance afforded me by Mr. Waterhouse of 

 the British Museum, in facilitating the task of inspecting the specimens in 

 that collection. To the President of the Geological Society I am also in- 

 debted for the prompt courtesy with which he has enabled me to avail 

 myself efficiently of illustrations from the valuable museum of that Society. 



I would take this opportunity of saying that I shall be greatly obliged 

 by any illustrations and opportunities similar to those which have already 

 been so kindly and liberally afforded to me. 



f See observations in the Ann. and Mag. of Nat. Hist. vol. xx. p. 337. 

 An interest beyond even that which they are calculated intrinsically to ex- 

 cite is thus given to these fossils, of the same nature as that which attaches 

 to a series of Ammonites from different beds. 



J Ante, p. 6. It is proper to state that there are many forms, besides 

 those thus specified, figured by Goldfuss as from the Jurakalk, and which 

 I have not much doubt are Ventriculidae. I have only enumerated the 

 more obvious. 



