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TERTIARY FAUNA OF FLORIDA 



valve, the posterior part being unfortunately defective. As in recent species 

 of Discinisca, the valve, viewed from below, is somewhat concave. 



FAMILY RHYCHONELLID^. 



Genus HEMTTHYRIS Orbigny. 



Hemithyris psittacea Gmelin. 



Anomia psittacea Gmelin, Syst. Nat., vi., p. 3349, 1792 ; Dillwyn, Descr. Cat. Rec. Sh., i., 



p. 293, 1817. 



Terebratula psittacea Lamarck, An. s. Vert., vi., p. 248, 1819. 

 Hemithyris psittacea Orbigny, Comptes Rendus, xxv., p. 268, 1847. 

 Rhynchonella psittacea Quenstedt, Handb. d. Petrefactenkunde, pi. xxxv., fig. 44, 1851. 



Fossil in the Pleistocene clays of the Gulf of St. Lawrence and New Eng- 

 land region as well as the bowlder clays of Alaska and northern Europe. Living 

 in the boreal seas of the whole northern hemisphere, both Atlantic, Pacific, and 

 Arctic. 



Genus RHYNCHONELLA Fischer de Waldheim. 



The following species differ from all the recent Hemithyris, Atretia, etc., 

 I have been able to examine in the character of the deltidium. In the type of 

 Hemithyris the deltidial plates are widely separated, and in the young are pro- 

 duced dorsally and even sometimes perceptibly recurved laterally. Under these 

 conditions the pedicle extends over an apex of the haemal or dorsal valve with 

 the deltidial plates at each side extending parallel to each other and the apex 

 of the ventral valve is recurved over them. In the older specimens the pro- 

 jecting deltidial edges appear to be worn away, and what little is added to the 

 plates extends towards the median line. 



In the first of the following species (and possibly in both) the deltidial 

 plates approach each other to form an arch, unite in the median line, and pro- 

 ject with flaring edges distally, thus forming a tube in which the peduncle is 

 enclosed and to which the beak of the ventral valve contributes a relatively 

 small portion. This arrangement is so different from that which obtains in 

 Hemithyris that I hesitate to include the species under that name, but, since 

 the internal characters are not accessible, prefer to list it under Rhynchonella 

 until more information shall be obtainable. 



Rhynchonella salpinx n. sp. 



PLATE 58, FIGURES 5, 6, 7. 



Eocene limestone of the city quarry, Wilmington, North Carolina; 

 Vaughan. 



Shell small, rounded trigonal, smooth behind, plicate anteriorly; ventral 



