PLATE LXIII. 



(Figures 1-3, 8-16, 21-28, 30, 33-30 by G. U. .SIMPSON; 4-7, 17-20, 29, 37. 44 by K. Emmons; 31, 32 by t\ B. Mkf.k; 38-43 



l)y U. P. Whitfield ) 



Genus PARASTROPHIA, gen. nov. 



Page 221. 

 PaRASTROPHIA IIEMIPLICATA, Hilll. 



Figs. 1, 3. Dorsal ami front views of an average specimen ; sliowing the eleviition of the plicated fold. 

 Fig. 2. Cardinal view of an internal cast ; shovifing- the median septa and .spondylia of both valves. 

 Trenton limestone. Jat-ksonbrn-qli , N. Y. 



PaRASTROPHIA DIVERGENS, .sp. IIOV. 



Fig. 4. Ventral view of an aversige specimen, somewhat worn in the umbonal region, exposing the spon- 

 dylinm and supporting septum. 



Fig. 5. Fi'ont view ; showing the elevation of the median fold and the low, spar.se plication 



Fig. 6. Dorsal view of the same si)ecimen, which has been so worn at the beak as to expose the convergent 

 walls of the spondylium. 



Fig. 7. Cardinal view of a specimen transversely sectioned in the umbonal region ; showing the spondylia. 

 In the shallower or pedicle-valve the median septum is very low and scarcely appai'ent, while 

 in the brachial valve the latei'al walls of the .spondylium, in this section, rest upon the bottom 

 of the valve. The crural plates arising from this spondylium are also shown. X 1^. 

 Hudson River group. WUmlngtoii, 1 Uliuns. 



Para.stkophia heversa, Billing.s. 



Figs. 8, 9, l(t, 14. Vf-ntral, protile, dorsal and cardinal views of the exterior of an average example ; showing 

 the relative convexity of the vah-es an<l the chai'acter of their plication. 



Fig. 11. Cardiniil view of a specimen which has been transversely sectioned in the umbonal region, the 

 l)racliial vahe being represented Iielow ; showing the spondylium of the jjedicle valve sup- 

 ]iorted by its median septum, and the septal plates of the bi'achial valve resting on the bottom 

 of the shell and suppiorting the crui'al apo]ihyses. 



Figs. 12, 13. Dorsal and ventral views of a smaller specimen ; showing the tine concentric lineation of the 

 surface. 



Clinton horizon. Island o/ Aiitiaixti. 



PaRASTROPHIA MULTIPLICATA, .sp. UOV. 



Figs. Ifi, 16. Anterior and profile views of an internal cast ; .showing the broad, strong plications <if which 

 there are four on the median fold jind three in the sinus. 



Fig. 2\. C'lrdinal view of another individual ; showing the casts of the spcmdyUa of the two valves, in the 

 brachial valve the lateral walls having rested upon the innei- surface of the shell. The mus- 

 cular scars of the brachial valve are also retained. 



Niagara dolomites. Near Milwaukee, TFm-o?m?j. 



PaRASTROPHIA GrEENII, sp. IIOV. 



Figs. 17, 18, 19, 20. Ventral, protile, dorsal and cardinal view of an internal cast; showing the character of 



the plication of the surface, and the median septum of each valve. 

 Fig. 22. Cardinal \iew of another and rather more convex internal cast ; showing the cavities left by the 



median se])ta. 



Niagai-a dolomites. Near Mihoaukee, Wisconsin. 



PaRASTROPHIA LATIPLICATA, sp. IIOV. 



Fig. 23. An internal ca.st of the brachial valve ; showing the few broad plications and the cavity of the 



median septum. 

 Fig. 24. An internal cast of the br.achia! valve in which the filling of the spondylium is exposed and the 



four scars of the adductoi' impression tlistinctly retained. 

 Figs. 25, 2t) Cardinal and profile views of the same specimen. 



Fig. 27. Anterior view of a specimen ; showing the elevation of the median fold, and the character of the 

 plication. 



Niagara dolomites. Near Milwaukee, Wisconsin. 

 The original specimens of this and the two preceding species are from the collection of Tuo.mas A. 

 Greene of Milwaukee. 



