98 AMERICAN JOURNAL 



of Breccia? In a country which has always been subjected 

 to volcanic disturbances, we should naturally look for the oc- 

 currence of some rock, like that of Wilmington, N. C, which 

 holds Eocene and Cretaceous species in common, and which is 

 of so uniform a character as to have deceived Professor Tuomey, 

 who imagined the Tertiary and Secondary species to have 

 lived in the same period.* Being a Breccia, the rock must have 

 been formed in the Eocene Period, and the exceptional char- 

 acter of its fauna is easily explained. Deshayes remarks of 

 the supposed intermixture of Cretaceous and Eocene fossils 

 in a transition formation in the Alps, "Leur melange a pu etre 

 le resultat de la degradation d'une couche marneuse fossillif^re 

 dans de la mer tertiare au moment de ses premiers depots." 

 Now, if Mr. Gabb really finds all his species which I consider 

 Eocene, in Division B, in company with Hamites and other 

 exclusively Cretaceous genera, how is it that, in his "Palaeon- 

 tology of California," he describes 13 Ammonites, 1 Belemnite, 

 1 Hamite, 3 Helicoceras^ 1 Turrilite, 1 Ptycoceras, 2 Crioceras, 

 1 Ancyloceras^ 2 Baculites ; not one of which is said to have 

 been taken from Division B, and only one Cretaceous genus 

 referred to that Division, — Aporrhais angulata {Anclmra, Con- 

 rad)? This, he says, occurs "in a single stratum of greenish- 

 gray limestone," so that its position in Division B is doubtful. 



With regard to the genus Atiiria^ it has not been found in 

 Europe, nor in America, east of the Rocky Mountains, nor in 

 Oregon, lower than the Older Eocene. Edwards says: "This 

 genus appears to be confined to the Tertiary, and is widely 

 diffused." 



Dosiniopsis aUa does not agree with Mr. Gabb's figure, the 

 posterior side being much shorter and more obtuse, and I be- 

 lieve it to be a difierent species. In Mr. Gabb's shell, the ex- 

 ternal character is so very close to Dosiniopsis Metldi^ that the 

 only difference is a more abrupt and sub-angular curve to the 

 anterior margin from the apex. Mr. Gabb says that his shell 

 is a true Dosinia; but he must publish a figure of the hinge 

 before he can substantiate the reference. The genus Dosinia 

 originated in the Miocene Period ; at least, it is yet unknown 

 in the Eocene, or in the Oligocene of America, and perhaps 

 of Europe. The form which closely resembles it externally, 

 is Dosiniopsis of the Older Eocene (Cyprinoid Cytherese of 

 Deshayes). 



In the beautiful illustrations to Dr. Karl Zittel's "Bivalves 

 der Gosaugebilde," the genus Cyprimeria is represented in 

 pi. 3, fig. 7, under the head of CVrce, and in pi. 4, fig. 1, as 



* The Lower Eocene beds of Jamaica contain masses of Cretaceous 

 limestone, and it may be that the California Lower Eocene strata contain 

 similar masses. 



