204 Dr. K. A. Grmwall — Dimijodon in British Mesozoic EocJcs. 



that this fossil belongs to Dimyodon, as this genus is represented by 

 the above-mentioned Cretaceous species. 



As it is obvious that this series of forms is v^idely distributed in 

 the Jurassic rocks of Great Britain, as well as in the Cretaceous, 

 I vs^ish to call the attention of British geologists to these fossils. 

 It would be a promising task to subject the genus and such allies 

 as may hide among the numerous obscure PlicatiilcB and Ostrece to 

 a thorough revision, but as I have neither the necessary time nor 

 material and literature at my disposal I will only give some hints 

 on this matter. 



The genus Dimyodon was established by Munier-Chalmas in the 

 "Manuel de Conchy liologie " of Fischer, 1887, p. 937, and its type 

 is D. Schlumbergeri, Mun.-Ch. (I.e., fig. 705), from the Bathonian of 

 Herouvillette. Fischer considers Dimyodon as a subgenus of Dimya 

 Eouault, but Zittel ^ seems to regard these two genera as identical. 



I am inclined to place the following species in the genus Dimyodon, 

 but, as already mentioned, this enumeration in no way claims to be 

 complete.- 



A. — Jurassic. 



1. D. intusstriatus, Emmr. A very widely distributed species in 

 the Ehaitic and the Lower Lias. In the Alps it was first found and 

 therefrom described by Emmrich ^ (the " Kossener Schichten " of the 

 Northern Alps). Its distribution in France is unknown to me, but 

 Mr. Jean Miquel, of Barroubio par Aiguesvives, has kindly 

 communicated to me a specimen from Villespanans (Herault) from 

 the Avictda contorta zone. As to its distribution in Great Britain, 

 I am indebted to Mr. Eichardson for very minute records; 

 D. intusstriatus has its maximum in the White Lias, but ranges from 

 the Avictda contorta zone to the Bucldandi zone. Mr. Eichardsou 

 has found it in Devon, Somerset, S. Gloucestershire, and Glamorgan- 

 shire. According to E. F. Tomes * it occurs also in Warwickshire. 



2. D. (?) retifer, Eudes-Deslongchamps. Mr. Miquel communicated 

 to me a specimen of this fossil (which I only refer to this species 

 on the faith of his determination) from the Upper Bathonian of 

 France, "falaise de St. Aubin sur mer, Calvados." It was determined 

 as a Flicatula, but there is no doubt of its belonging to Dimyodon. 



3. D. ScJilumbergeri, Munier-Chalmas. This species, the genotype, 

 is found in the Bathonian of Herouvillette, France, and is figured 

 in Fischer's " Manuel de Conchy liologie " (I.e.). 



4. D. striatissimus, Quenstedt,* from the Malm of Germany, White 

 Jura 7. 



1 " Grundziige d. Palaontologie," Zweite Auflage, 1903, p. 292. 



* Besides that some species may be concealed among Flicatulce and Ostrece, I may 

 here mention that Mr. Munier-Chalmas in 1897 told me, in a letter, that there were 

 still some undescribed Jui'assic species of Dimyodon. 



' Jahrb. d. k. k. geol. Reichsanst., vol. iv (1853), p. 376. 



4 Q.J.G.S., vol. xxxiv (1878), p. 182. 



5 "Der Jura," 1858, p. 628, pi. Ixxviii, fig. 4. The author also figures 

 a Flicatula sp. (pi. Ixxviii, fig. 5) from the AVhite jura /3 ; it belongs to Dimyodon. 



