148 



ON THE GENERA OF VENERID^ REPRESENTED IN THE 



CRETACEOUS AND OLDER TERTIARY DEPOSITS. 



By A. J. Jukes-Beowne, B.A., F.G.S. 



Mead I2th June, 1908. 

 PLATE VI. 



I. Introductory Remarks. 

 Having being led to study the shells of the recent species of the 

 family Veneridse, with the view of revising the many generic and 

 snbgeneric groups which have been proposed by various writers, and 

 of constructing more satisfactory definitions of them than exist in any 

 current textbooks, I found that it was necessary to include the fossil 

 representatives of the family within the scope of my review. 



The family doubtless originated during the course of Jurassic time, 

 but it is doubtful whether any representatives of it exist among the 

 Jurassic faunas of England or of Northern France. Several genera, 

 however, make their appearance in the Lower Cretaceous rocks of 

 both countries, and a still greater variety of forms is found in the 

 Eocene series. 



It would be interesting to ascertain whether the Veneridse developed 

 from one centre, or along two different lines of descent ; the possibility 

 of the latter mode of origin being suggested by the great difference 

 which is observable among the Cretaceous representatives. Dosmiopsts, 

 for instance, by its possession of posterior lateral teeth is unquestionably 

 a link between Cyprina and Dosinia, while the Tapesine genus Baroda, 

 by its elongate shape and by the simplicity of its hinge-teeth, seems 

 to have had a very different origin. 



With regard to the later Tertiary species (of Pliocene and Pleisto- 

 cene age), most of them can be referred without difficulty to recent 

 genera, but some of the Eocene and Cretaceous species exhibit differences 

 which make it necessary to regard them as distinct genera or sub- 

 genera, while at the same time they illustrate the lines along which 

 the recent genera have developed. 



In this paper I shall concern myself with those species of Cretaceous, 

 Eocene, and Oligocene age which occur within the limits of the Anglo - 

 Parisian region, i.e. in the South of England and the North of France. 

 In our own country palaeontologists have hitherto been content to 

 catalogue the British species under the names of Venus and Cytherea 

 (or Meretrix), and up to about 1885 French palseontologists were 

 content with the same generic nomenclature, except that Deshayes 

 had described two species of Tapes, several supposed Venerupis, and 

 a shell to which he gave the generic name of Psathura. In 1886, 

 however, the Veneridse of the Parisian Eocene were the subject of 

 careful study and description by M. Maurice Cossmann, who recognized 

 eleven different genera, of which number three were new, and he also 

 divided his genus Cytherea into five sections or subgenera, and his 

 Venus into three. ^ 



1 Ann. Soc. Roy. Mai. Belg., torn, xxi, p. 104. 



