BRACHIOPODA—ATREMATA. 193 



11. L. aurora Hall. Upper Cambric. 

 Broadly ovate; breadth about x / 2 inch, length somewhat greater. 



Pedicle valve with beak slightly attenuate, cardinal area high. 

 Brachial valve with very obtuse beak. Surface marked by concen- 

 tric striae crossed in partially exfoliated specimens by radiating striae. 

 St. Croix of Wisconsin, Minnesota. 



12. L. (Westonia) ella (Hall and Whitf.) (Fig. 229. a, b. 



Lower-Middle Cambric. 



Brachial valve subcircular or ovate; pedicle valve longer than 

 wide, cardinal slopes about 65 degrees (greater when compressed); 

 area flattened, rather broad and with narrow median groove. 

 Growth lines lamellose towards the front ; radiating lines indistinct. 



Wasatch and Oquirrh . Mountains, Utah; near Pioche, Nevada. 



VII. Lingulepis Hall. 



Lingula-like but strongly inequivalved. Pedicle valve generally 

 much produced at the beak. Differs from Lingulella in the absence 

 of a distinct cardinal area and 

 in the often much attenuated 

 beak of the pedicle valve. Up- 

 per Cambric-Ordovicic. 



13. L. pinniformis (Owen). 

 (Fig. 227.) Upper Cambric. |, H Ij 

 Pedicle valve spatulate ; pos- ^^ISHP 



terior portion attenuate, acute, J^^^^" . . . r 



Fig. 227. Lingulepis pinniformis in- 



convex in the middle. Anterior ternal molds of . pedicle and brachial valves , 

 portion semicircular. Brachial x 2. (After Hall.) 

 valve without the attenuate por- 

 tion. Surface of both valves marked with concentric striae and 

 where exfoliated, with faint radiating ones. 



St. Croix of Wisconsin, South Dakota. Potsdam of New York 

 and Canada (Z. acuminata). 



14. L. prima (Hall.) Upper Cambric. 

 Valves moderately convex with rounded front. Umbo very low. 



Surface marked by a few concentric wrinkles and by many fine 

 longitudinal lines. An average shell measures ]^ inch by \ inch 

 in length and breadth respectively. 



Potsdam of New York, South Dakota. 



