PLATE XX— Continaed. 



ANOPLIA, SUB-GEN. NOV. 



Page 309. 



Anoplia nucleata, Hull. 



(See Plate XVIIa, fig-s. 17, 18.) 



Fig. 14. Internal cast of a pedicle-valve ; showing- the impression of the short median septum, and the pns- 



tulose character of the pallial region. X 3. 

 Fig. 15. The interior of a brachial valve ; showing the muscular impre.ssion and the pustnlose surface. 



The cardinal process is bilobed, but is pi'obably shorter than is noi-mal for the species. X 3. 

 Fig. 16. The exterior of the brachial valve; showing the smooth surface. X 3. 



Oi'iskany sandstone. Jones cmmity, Illinois. 

 Fig. 17. The central cardinal portion of an internal cast of the pedicle-valve ; showing the filling of the ob- 

 lique cai-dinal tubes which do not jaenetrate to the external surface. X 6. 

 Oriskany sandstone. Columbia county, iV. T. 



CHRISTIANIA. gen. nov. 



Page 298. 



Christiania subquadrata, Hall. 



(See Plates XV and XVIIa.) 

 Figs. 18, 19. Two views of the pedicle-valve ; showing its elongate form, incurvature and smooth or squam- 

 ous exterior. X 2. 



Fig. 20. The exterior of the brachial valve, which shows the cardinal process and edges of the crural 

 plates. X 2. 



Lower Helderberg group. Ferry county, Tentiessee. 



LEPT^NA, Dalman. 



Page 276. 

 LEPTiENA RHOMBOIDALIS, WilckeilS. 

 (See Plates VIII and XVIIa.) 

 Fig. 21. The deltidial area of both valves of a small individual. X 3. 

 Fig. 21a. Longitudinal section of the two valves; showing the degree of curvature. 



Fig. 22. The interior of a brachial valve ; showing very distinctly the division into anteiior and posterior 

 muscular scars. 



Hudson River group. Cincinnati, Ohio. 

 Fig. 23. The interior of a brachial valve, in which the margins of the broad posterior adductors have be- 

 come elevated into fi'ee alate extensions. X 2. 

 Niagara group. WalAron, Indiana. 

 Fig. 24. The muscular ai-ea of the brachial valve, figured on Plate VIII (fig. 31) ; enlarged from a gutta- 

 percha impression. The area is subdivided into three paii-s of scars, the elongate central pair 

 being probably accessory to the posterioi- adductors. X 3. 

 Waverly group. Medina county, Ohio. 



LEPTiENA ? uNicosTATA, Meek and Wortheu. 



See Plate XVIIa, fig. 89. 



Figs. 25, 25a. The interior of a brachial valve and cardinal ai-ea of a pedicle-valve ; showing characters of 



LEPT.a!NA. 



Hudson River group. Ohio. 



STROPHOMENA, Rafinesque (de Blainville). 



Page 245. 



Strophomena WiNcfiELLi, sp. nov. 



(See Plate I'X, fig. 12.) 

 Fig. 26. An enlargement of the muscular area of the brachial valve cited ; showing the broad posterior and 

 elongate anterior scars. X 3. 



Trenton limestone. Janesville, WiscoTisin. 



