34 



PROCEEDINGS OF THE ACADEMY OF 



[Part I 



Diplodon wanneri n. sp. Plate III, fig. 5. 



The shell is oblong, compressed, with small beaks, but little pro- 

 jecting, at about the anterior fourth of the length. The dorsal 

 outline is moderately arched; anterior end evenly rounded, posterior 

 end somewhat oblique, rounded; basal margin straightened. The 

 posterior ridge is prominent but rounded. Surface is smooth, ex- 

 cept for unequal wrinkles of growth. There is a gray- white cal- 

 careous layer about the thickness of writing paper, covering the 

 shell like a periostracum (broken away in places). The interior 

 is unknown. 



Length 37 mm.; alt. 22 mm.; diam. 11.7 mm. 



No traces of beak sculpture are discernible in the type specimen, 

 which, as mentioned above, is covered with a thin layer of calcite. 

 A much flattened specimen shows the beak sculpture (fig. 6) . There 

 are fine corrugations diverging from the posterior ridge, gradually 

 weakening, and finally disappearing about 17 mm. from the beak. 

 In the median part of the valve the fine corrugations radiating 



Fig. 6. — Beak sculpture of Diplodon wanneri, paratype. 



Diagrammatic. 



from the beaks are gently curved towards the middle, though only 

 a few of them meet (Hyria fashion). The branching of the corru- 

 gations produces some faint appearance of zigzag pattern in the 

 middle. In this region the sculpture reaches only about three or 

 four mm. from the beaks. Total length of this shell is about 33 mm. 

 Locality: Shale, Little Conewago Creek (loc. 5). 



Diplodon carolus-simpsoni n. sp. Plate II, figs. 4, 5, 6. 



The type is a left valve, imperfect in the anterior-basal region, 

 with part of the right valve almost wholly imbedded in the hard, 

 dark gray shale. 



The_ shell is oblong, plump, rather thick (1.6 mm. at about the 

 posterior third). The beaks are full and prominent, near the an- 

 terior end, which is rounded. Posterior end is oblique, being pro- 

 duced at the post-basal extremity. The posterior ridge is prominent 

 and rounded. Sculpture of rather strongly marked lines and wrinkles 



