Raymond : Gastropoda of the Chazy Formation. 197 



Genus Oxydiscus Koken. 



Oxydiscus catilloides Raymond. 



(Plate LV, figures 9, 10.) 

 Bucania catilloides Raymond, 1906, Annals Carnegie Museum, Vol. 

 Ill, p. 576. 



Description. 



Shell very small, compressed, with two or three whorls which 

 expand gradually. The carina is narrow, but distinct and elevated. 

 The form is much like that of Oxydiscus acutus (Sowerby), but the 

 umbilicus is wide enough to expose all whorls. On none of the 

 specimens are the surface markings preserved. 



Locality. — A very rare fossil in the Chazy, found only on the west 

 side of Valcour Island where it is associated with Bucania sulcatina, 

 Zygospira aculirostris, and species of Phylloporina. 



The type is in the Carnegie Museum. 



Genus Tetranota Ulrich and Scofield. 

 Tetranota bidorsata? (Hall). 



(Plate L, figure 5.) 

 Bucania bidorsata? Raymond, 1906, Annals Carnegie Museum, Vol. 



Ill, part 4, p. 514 et sea. (In faunal lists.) 



From a layer of decomposed limestone on the south end of Valcour 

 Island, a considerable number of imperfect specimens of a species of 

 Tetranota have been obtained. All are casts of the inner whorls, and 

 are not sufficiently well preserved to permit ot accurate identification, 

 but they appear to be closely related to Tetranota bidorsata. 



Description. 



Shell small, closely coiled in one plane, umbilicated on both sides. 

 Surface of the cast, which shows only the inner whorls, marked by 

 four keels, two marginal and nearly obsolete, two central and con- 

 nected by a flat or slightly concave band. The shells show no other 

 surface markings and the form of the aperture is not shown. 



These shells may be compared with either Tetranota bidorsata (Hall) 

 or Tetranota obsoleta Ulrich and Scofield. It differs from the former 

 species in having the revolving keels less strongly developed on the 



