70 PROCEEDINGS OP THE ACADEMY OP 



The genera Lavinia, Siboma, Algansea, Tigoma, Cheonda, Gila, Ptycho* 

 chilus aad Mylochilus, are closely related to each other, and cannot be dis- 

 tributed among different subfamilies, as has been attempted. Indeed, some 

 of the genera so separated are so intimately allied, that their claims to generic 

 distinction are extremely doubtful. Siboma appears to be nearly allied to 

 Lavinia, and includes only the S. crassicauda, the <S. atraria belonging rather 

 to Algansea. Algansea itself and Tigoma are scarcely distinguishable, they 

 differing only in the pharyngeal teeth, Algawea having teeth 5 5, increas- 

 ing upwards, while Tigoma has, normally, 2 | 5 5 | 2 : both groups have 

 narrow suborbitals. Cheonda should be restricted to C. Cooper i. The dif- 

 ference between C. cozrulea and species of Tigoma are not evident. Gila and 

 Ptyrhochiius both require revision. Mylochilus and Mylopharodon do not dif- 

 fer generically, wherefore the former name alone can be retained. The genus 

 Acrochilus of Agassiz, referred to Lavinia by Girard, has no affinity to that 

 group, being nearly related to Ckondrostoma, as shown by Agassiz, who has 

 well described its peculiarities, while Lavinia as well as Tigoma, Algansea, 

 &c, are closely related to the European Leucisci. As I propose, on another 

 occasion, to give the full generic characters, as well as anatomy of the genera 

 of Western American Cyprinoids, I defer till then further consideration of 

 their affinities. 



Observations on the EOCENE LIGNITE FORMATION of the United States. 



BY T. A. CONRAD. 



OLDER EOCENE OR LONDON CLAY. 



Lignite Epoch. 



Some years ago I visited a marl deposit near Long Branch, Monmouth Co., 

 New Jersey, in which casts of a few shells presented an eocene character. 

 Observing in Vanuxem's cabinet a specimen of what is now known to be 

 Aturia ziczac, I described it in the Journal of the Academy of Natural Sci- 

 ences, vol. i. 2d series, p. 129, and referred the marl, principally on account 

 of the presence of this shell, to the eocene era. I also described an imperfect 

 cast of the same species as Nautilus angustatus, in Dana's Report on the Ge- 

 ology of the Exploring Expedition, which was found at Astoria in Oregon, in 

 company with many shells which I mistook for miocene forms ; but a more 

 extended acquaintance with eocene types shows their older tertiary relations, 

 and their matrix to be synchronous with the Loudon Clay of Sheppey, High- 

 gate and Bracklesham. Professor Cook has lately sent me a box of specimens 

 of similar age from Shark River, Monmouth Co., N. Jersey, collected by Dr. 

 Kneiskem. In company with Aturia ziczac there are imperfect specimens of 

 Nautilus Lamarclcii, Deshayes, another older eocene form of the Paris basin 

 and of Belgium. Fruits also occur in this bed, referrible to the genera Nipa- 

 dites and Mimo sites, showing the tropical or semitropical climate of the era, 

 and giving evidence of the intimate relations of the deposit to the Brandon 

 and Mississippi Lignite strata. Indeed, it seems clear that this Shark River 

 marl was the bed of the oldest eocene ocean, and that the flora of the Bran- 

 don and Southern tertiary epoch flourished at the same time. The local, 

 circumscribed character of the Brandon Lignite is attributed by Prof. Lesley 

 to its having filled a deep depression, thus escaping the denuding forces 

 which swept all traces of it away over a wide region that it once covered. 

 The locality at Mont Alto, near Chambersburg, described by Prof. Lesley, is 

 doubtless a locally preserved fragment of a vast formation once deposited 

 over the Appalachian slope to the very base of the mountain range, and oc- 

 cupying a large space in South Carolina, Georgia, Alabama and Mississippi, 

 and in fact, extending to the Pacific as far north as Vancouver's Island. 



[April, 



