286 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxvm. 



PROTORTHIS WINGI, new species. 



General form traiisvers(>ly suhelliptical. Surface marked l)v about 

 20 sharply ridged ril)s with interspaces equal and usually greater than 

 the width of the rib; shell with numerous small and many larger and 

 scattered punctie on the inner and outer surfaces. The largest ventral 

 valve has a length of 6 mm. ; width, nnu. 



Ventral valve convex, elevated at the umbo and beak; area high 

 and divided midway by a strong delthyrium which is partially closed 

 by a concave free spondylium as in JR. hiJlhir/.'^i, teeth strong, dental 

 plates extended toward the center to unite and form the free spon- 

 dylium. 



Dorsal valve slightly convex, with a broad median sinus that is 

 usually bounded by one or two large ribs; casts of the interior show a 

 narrow area, broad delthyrium, and the cast of a siuall, l)roadly trian- 

 gular, elevated area opposite the umbo that probal»l\" served as the 

 cardinal process for the attachment of the diductor muscles. 



Ohisercatio)is. — This species is most nearly related to Protorthls 

 'lumtes; it differs, as far as known, in the character of the interior of 

 the dorsal valve, the large puncta^ scattered among the tine punctii?, 

 and the sharp ridged ribs. One cast of an interior of a ventral valve 

 appears to indicate that that shell Avas without the free spond^dium. 

 It not infrequently occurs in Protoi thU IvUhuj.si that the free spondyl- 

 ium is reduced to a narrow rim aV)out the margin of the delthyrium, 

 and it may ))e that in this shell it was al)sent. 



The specific name is given in memory of Rev. Augustus Wing, who 

 did so much excellent work in the vicinity of Swanton, Vermont, 

 which was utilized by Mr. Billings and Sir William E. Logan. 



Forviation and Jocdh'fif. — Upper Cam)>rian. Dark argillaceous 

 shales, about one-half mile south of llighgate Falls, Vermont. 



PROTORTHIS, species undetermined. 



Ventral valve convex, elevated at the undio, apex incurved. The 

 cast of the umbonal cavitv (pseudospondylium) indicates well devel- 

 oped teeth and dental plates. On the cast 6 radiating ribs occur in 

 the distance of i nun.: area aV)out vertical. The surface of the cast 

 indicates that the interior layer of the shell was lineh' pimctate. 

 Length of valve 4.5 nun., width 5.5 mm. 



Only one specimen of a cast of a ventral valve of this shell was 

 found. It suggests by its convexity and surface some of the more 

 convex forms of Protarthis qnacoensis. 



Formation and locality. — Vr\^^^^x Cambrian. Tonto terrane. Thin 

 bedded siliceous limestone at mouth of Kanab Canyon, Grand Canyon, 

 Arizona. 



