TRANSACTIONS OF WAGNER 

 1458 



TERTIARY FAUNA OF FLORIDA 



dinal teeth has gone far enough to separate those of the right valve, which in 

 the typical section remain united. 



Subgenus Musculkim Link. Type 5". lacustre Miiller (as Tellina). 



Nepionic valves inflated, concentrically finely striated, marked off from the 

 adult growth by a distinct sulcus ; ligament partly covered ; cardinal teeth 

 minute, often obsolete, continuous in the right valve. 



This group is usually called Calyculina Clessin. The prominence of the 

 calyculate umbones varies in different species. 



Sphczrium occurs in most of the western freshwater Tertiaries, in the loess 

 of the Mississippi Valley, and in Pleistocene marls over the whole continent, 

 but the species have been little studied. 



The earliest recorded species are from the upper Cretaceous or lower Eocene 

 of the Laramie beds, from which Meek and Hayden have described S. planum, 

 S. recticardinale, S. formosum, S. snbelliptiaim, and 5'. fragile* From beds 

 referred to the Miocene in Utah Meek has named .S". rugosum and 5". idahoense. 

 From the loess of Iowa City, Iowa, Shimek has recorded 6". sulcatum Lam., 

 S. solidulum Prime, and 5". striatinum Lam. From the marls of Huron County, 

 Michigan, Bryant Walker enumerates .S". striatinum Lam., 6". simile Say, 5". 

 securis Prime, S. rhomboideum Say, 5". occidentale Prime, 5'. partumeimn Say, 

 and S. truncatum Linsley. From near Milwaukee, Wisconsin, F. C. Baker has 

 collected out of a Pleistocene marl 5". simile Say and 5'. rhomboideum Say. The 

 interglacial beds of the Don Valley near Toronto, Canada, yielded to Professor 

 A. P. Coleman 5". rhomboideum, striatinum, sulcatum, solidulum, and simile. 

 These lists might be considerably added to if the literature of the Pleistocene 

 should be exhaustively searched. 



Notwithstanding the presence of Sphcerium in the interglacial beds above 

 noted, it has not, so far, appeared in the Alaskan Pleistocene marls or those 

 of the Hudson Bay region, though Anodonta and Corneocyclas occur abun- 

 dantly. 

 Subgenus Eupera Bourguignat. Type Pisidium Moquiniaimm Bourguignat. 



Shell subrhomboidal, moderately inflated, thin, with the posterior side 

 longer, the ligament partly exposed, the cardinal teeth feeble, reduced to a 

 single pustular denticle in each valve ; the laterals elongated, strong, double 

 in the right, single in the left valve. Limosina Clessin is synonymous. 



* Not S. fragile Clessin, in Westerlund, 1890, from near Vegesack, in North Ger- 

 many, which may take the name of S. tenellum. 



