3fesozoic and Cceiwzoic Geology and Palaeontology. 87 



Gemma cretacea; and from Haddonfield, New Jersey,* ^ora cretacea, 

 Tenea parilis^ ^rEnona i^apyria, Venilia elevata, now Veniella elevata, 

 Cardium dumosum, and Solyma lineolatus. 



In 1871, Prof. F. B. Meekf said, the oldest beds of the Bear river 

 country of Utah and Wyoming, properly belonging to the Tertiar}', 

 (tiiey are now regarded as Cretaceous), and so intimately I'elated to 

 the latest Cretaceous, contain species of Corbula, Cyrena {Corhicula) 

 perhaps Ostrea, and a univalve related to Mela^aj'xi'S, directly asso- 

 ciated with several species of (TO/i/'o6a.9ts, two of Unio, one or two of 

 Melantho, several species of Viviparus, one of Tiara, etc., showing 

 clearly that these strata were deposited in brackish waters. These 

 shells also exist in great numbers, and are preserved in a condition, 

 showing that they could not have been transported far by currents, 

 but that they must have lived and died, at least, near where we now 

 find them. 



All palaiontologists are aware of the fact, that the remains of fresh 

 and brackish water shells do not generally present such well marked 

 peculiarities ot form, ornamentation, etc., in beds of different ages, as 

 we see in marine types, so that they can not always be relied upon, with 

 the same degree of confidence in identifving strata, that we place in 

 marine forms; some of those from oldest Cretaceous being, for instance, 

 very similar to existing species. So far as I have been able to com- 

 pare the species from this formation with described forms from other 

 parts of the woi'ld, they generally agree most nearly with Lower 

 Eocene types; the Corbicrda and Tiara being very similar to forms 

 found in the lower lignites of the Paris basin, and at the mouth of 

 the Rhone in France. At the same time it is worthy of note, that most 

 of these shells are quite unlike any of the known existing North 

 American species, and one of them [Tiara humerosa) belongs even to 

 a oenus entirelv unknown among the existing Melania of the American 

 continent, though found inhabiting the streams of Madagascar, the 

 Fejee Islands, etc. One of the Uniones ( U. helllplicatvs) resembles in 

 its ornamentation some of the South American species, and the genus 

 Castalia, much more «early than it does any of the recent North 

 American species, although having the form and hinge of a true Unio: 

 and another abundant bivalve, found in the same association, Corbula 

 [Anisothyris) pyriformis, seems to be allied in some respects to a 

 peculiar group recently described from a Pliocene or Miocene forma- 

 tion, on the Upper Amazon of South America, by Mr. Gabb, under the 



'■' Am. Jour. Conch., vol. fi. 



t Advance pamphlet from Hayden's U. S- Geo. Sur of Wyoming, etc. 



