PLATE LXIII. 



(r»fM»I-«,»-l«,U-«,ao,SJ-S8byO. B. 8l¥P»oi»; 4-7. I7-». ». »7, « by E. Emhons; SI.Mby K. B. Mefk; 88-13 



by K. I". WHITFIELD ) 



Genus PAKASTliOPHIA, gen. nov. 



Page »1. 



Parastrophia hemiplicata, Hall. 



Figs. 1, 3 Dorwal and front views of an avt-rayi; njjecinu'n ; showing- the elevation of the plicated fold. 

 Fl». 8. Cardinal view of an internal cast ; showinjf the median septa and spondylia of both valves. 

 Trenton limestone. J(u-ksonlmrgh, N. Y. 



Parastrophia diveroens, sp. nov. 



^g, 4. Ventral view of an averagtj specimen, somewhat worn in the umbonal region, exposing- the spon- 

 dyliiun and snpjiorting septum. 



Vig. 6. Front view ; showing- the elevation of the median fold and the low, sparse plication 



Fig-. 6. Dorsal view of the same s])ecimen, which has been so worn at the beak as to exjiose the convei-gent 

 walls of the spomljlium. 



Kip. 7. Cardinal view of a specimen transvei-sely 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 lateral walls of the spondyliuni, in this section, rest upon the bottom 

 of the valve. The criu^l plates arising from this spondylinm are also shown. X 14- 

 Hudson River grouj). fVilmiugton, I lliiuiis. 



Parastrophia reveksa, Billings. 



Figs. 8, 9, 10, 14. Ventral, profile, dorsal an<l canlinal views of the exterior of an avei-age example ; showing 

 the relative convexity of the valves and the character of their plication. 



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

 brachial valve being i-epi-esented below ; showing the spondylium of the jiedicle valve sup- 

 jx)rted by its median septum, and the septal plates of the brachial \alve resting on the bottom 

 of the shell and supporting the crural aj)ophyses. 



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

 surface. 



Clinton horizon. Island of AvHcostl. 



Parastrophia multipligata, sp. nov. 



Figs. 15, 16. Anterior and i)rotile views of an intenial cast ; showing the broad, strong plications of which 

 there are four on the me<lian fold and thi-ee in the sinus. 



Fig. 21. Canlinal view of another individiml ; showing the ca-sts of the spondylia of the two valves, in the 

 brachial valve the lateral walls ha\-ing resteil upon the inner surface of the shell. The mus- 

 cular scars of the brachial valve are al.«o n-tained. 



Niaj^ara dolomites. Near Mihoaakee, IVUconain. 



Parastrophia Greenii, sp. nov. 



Figs. 17, 18, 19, 20. Ventral, profile, dorsal and cardinal view of an intei'nal cast ; showing the character of 



the ]ilication of the surface, anct the median septum of each valve. 

 Fig. 22. Canlinal view of another and rather more convex internal cast ; showing the cavities left by the 



median septa. 



Niagara dolomites. Near Milwaukee, WiscoTisin. 



Parastrophia latiplicata, sp. nov. 



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



median septum. 

 Fig. 24. An internal cast of the V>rachia! valve in which the filling of the spondylium is exposed and the 



four scars of the adductor impression <listinctly retained. 

 Kiirw. 2.5, 2t( Canlinal ami jirofile views of the same specimen. 



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

 ]>lication. 



Niagara <lolomites. Near Milwaukee, Wiscongin. 

 The original sjwcimens of this and the two preceding species are from the collection of Thomas A. 

 Qbkbmk of Milwaukee. 



