PLATE XV A. 



(Figures 1-lS, 20-2: 



, -24-28, M, 40, 43 by E. Emmons; 19, '23, 34, 35, 37, 38 bv G. B. Simpson; 29, 30 bv J. M. Clarke; 41, 42 

 by C. E, Beecher; 31-33 copies.) 



Legend. 



D. 

 C. 

 ps. 

 F. 



t. 



a. 

 1. 



Deltidiiim (pedide-valve). 



Deltidium (brachial valve). 



Pedicle-.sheath. 



Koranieii 



Teeth. 



Dental lamellae. 



Spondyliuni. 



j. Cardinal process. 



c. Crura, 



br. Brachial ridijes. 



a. Anterior adductor scars, 



a'. Posterior adductor scars. 



r. Diductor seal's. 



X. Scar'of attachment. 



Genus CLITAMBONITES, Pander. 



Clitambonites Verneuili. (voii 



(See Plate VII.) 

 rage 233. 



Eiclnvald) Billiuff.s (== Hemipronilen Americannx, 

 Whitfield). 



Figure 2 shows that the deltidium has been lost, exposing 



showing the concave delthy- 



Figs. 1, 2. Opposite sides of conjoined valves. 



the spondyllum. 

 Fig. 3. The interior of a pedicle-valve which does not retain the deltidium ; 



rial plate or spondyliuni supported by a median septum. 

 Fig. 4. A view of the same specimen, looking into the umbonal ca%-ity of the valve. 



Trenton horizon. Cannon Falls, Minnesota. 

 Figs. 5, R. Interiors of brachial valves; showing the simple cardinal process abutting against the deltidium, 

 and the quadripartite impression of the adductor muscles. 

 Trenton horizon. Island of Anticosti. 

 Figs. 7. 8. Profile and cardinal views of a small pyramidal specimen which may be a variety of this spe- 

 cies. The deltidia of both valves are retained, that of the pedi<'le-valve being perforated by a 

 large foramen. 



Trenton horizon. Cannon Falls, Minnesota. 



Fig. 



Genus HIPPARIONYX, Vanuxem. 



(See Plate IX.) 

 Page -257. 



HiPPARiONYX PROXiMUS, Vauuxeiii. 

 The interior of a pedicle-valve di'awn from a gutta-percha impression of a natural mould ; show- 



ing the character of the cardinal area and dental lamelLne. the gr'eat size of diductor scars, the 

 margins of which are thickened ami elevated by the deposition of testaceous matter. The 

 surface of the elevations thus formed is strongly pitted. The specimen also shows the low 

 median septum diviiling the adductor impression." which in the umbonal region unites with the 

 dental lamelUe to foi'm an apical callosity. 

 Fig. 10. The cardinal process and crural jilates of the brachial valve. The ci'enulations of the marfrin of 

 the valve are seen to extend almost to the base of the process. 

 Oi'iskany sandstone. Albany county. iV. T. 

 Fig. 11. Profile of an internal cast of the two valves. The specimen is drawn with the brachial valve above 

 and shows the relative convexity of the v.alves and the extent of the crenulated margin toward 

 the apices. 



Oriskany sandstone. Cayuga, Province of Ontario. 

 For further illustr.ation, see Palieontology of New York, Volume III, plates 89, 90. 



Genu'^ LEPTELLA, gen. nov. 



Page 293. 



Leptella sordida, Billings (sp.). 



Figs. 12, 13. Two views cf a specimen retaining Vioth valves, and showing the outline, contour and general 

 external characters of the species." The delthyrium of the pedicle-valve is partially closed by 

 a convex delliilium. X '^, 

 14. The interior of a pedicle-valve ; showing the cardinal area, deltidium and teeth, but no trace of 

 the muscular scars is retained. X 3. 



Fig. 



