NEWTON : CONCHOLOGICAL FEATURES OK LKNHAM SANDSTONES. I4I 



OSTREA PRINCEPS S. V. Wood. 



Fig. 16. — An external view of a small example of this si)ecies, occurr- 

 ing as a sandstone cavity, showing the strong, squamose 

 radial costse. From a gutta-percha model. 



[M.P.G., No. 402]. 



Barnea cylindrica J. Sowerby, sp. 

 Fig. 17. — A fragmentary right valve of small size, showing its cylind- 

 rical contour and the elongate-concentric ridges crossed by 

 fine striations and best seen at the anterior end. From a 

 gutta-percha model, x i'^. [M.P. G., No. C.R. 1274]. 



Yoldia oblongoides S. V. Wood, sp. 

 Fig. 18. — Natural sandstone cast of fragmentary left valve, showing 

 the minute denticles on each side of the umbo, x 2. 



Fig. ig. — xA similar cast of a right valve. 



[B.M., Graham Wallas Coll.]. 

 Fig. 20. — External view of a right valve, with concentric growth-lines. 

 From a gutta-percha model. [M.P.G., No. 426]. 



PLATE 3. 

 Gastropoda (extinct). 

 Streptochetus sexcostatus Beyrich, sp. 

 Fig. I. — Dorsal view of specimen showing the equi-distant and con- 

 vex longitudinal costse and the spirally threaded ornamenta- 

 tion of the whorls. From a gutta-percha model, x 2. 



[M.P.G., No. 469]. 

 Fig. 2. — Latero-dorsal aspect of another specimen. From a gutta- 

 percha model, x 2. [M.P.G., No. 451]. 



Ptychopotamides tricinctus Brocchi, sp. 

 Fig. J. — View of specimen showing the triple rows of granulations on 

 each whorl. From a wax impression. [B.M., Kennard Coll.]. 



Drillia obeliscus Des Moulins. 



Fig. 4. — Lateral view showing the longitudinal costce crossed by fine 

 spiral striations, and the narrowly banded suture. From a 

 gutta-percha model. [M.P.G., No. 459]. 



Fig. 5. — Enlarged view of same specimen, x 2. 



Fig. 6. — Another and more slender example of the same species. 

 From a wax impression. [B.I\I., Graham Wallas Coll.]. 



Eumargarita trochoidea S. V. Wood. 

 Fig. 7. — Summit view exhibiting four volutions. 



