604 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxv. 



The interior of the pedicle valve shows a cardinal scar on each .side, 

 well out toward the lateral margin, which corresponds to the position 

 of the transmedian and antero-lateral scars in Oholus ajJoUinis. The 

 visceral area is small and compressed between the sinuses occupied by 

 the large, main vascular canals. The opening of the foraminal tube 

 is oval and situated at the posterior portion of the visceral depression 

 at the margin of the area. The main vascular canals start near the 

 beak and gradually diverge toward the antero-lateral margins of the 

 valve. The interiors of the brachial valve associated with the two 

 pedicle valves illustrated are all so imperfect that only a median 

 ridge like that in Acrotreta can be clearly determined. This ridge 

 varies greatl}' in size and length in ditierent specimens. 



Oh.^er vat tons. — In a hast}' examination of this species in 1884, Icon- 

 fused the dorsal valve Avith that of Acrotreta and considered the ventral 

 valve as the type, placing it under Lingulepw., stating that it had 

 "nearly the same vertical range and geographic distribution as L. 

 tnaeraP As now known, it is confined to the one localit}' discovered by 

 the geologists of the Fortieth Parallel Survey, and to a single slab of 

 reddish-brown sand}^ shale on which a large number of the separated 

 valves occur. 



The generic reference is somewhat doubtful on account of the difler- 

 ence in what is known of the interior of the dorsal valve and the position 

 of the area of the ventral vah'e. 



Formation and locality. — Upper Cambrian, Hamburg Ridge. Eureka 

 district, Nevada. 



LINNARSSONELLA TENNESSEENSIS, new species. 



General form of pedicle valve rounded subtriangular, moderately 

 convex, with the beak curving gentlv over a ver}- low false area nearly 

 to the posterior margin. Foraminal opening minute and situated a 

 little in front of the beak. Brachial valve moderately convex, with the 

 beak marginal. 



Surface of shell marked by fine concentric striie and lines of growth. 

 The interior surface shows a few fine radiating stria^. Shell rather 

 thick and built up of several thin layers or lamellte. 



The cast of the interior of the pedicle valve shows small cardinal 

 scars and a minute foraminal tube directed backward very much as in 

 Oholella atlantlca. The main vascular canals of the pedicle valve are 

 outlined nearh^ to the antero-lateral margins and include between 

 them a narrow visceral area. The cast of the brachial valve indicates 

 relatively strong cardinal scars, distinct central scars, and a narrow 

 median ridge. None of the specimens show the main vascular canals 

 except at their base. 



OhMerrations. — Thi.s shell has the general outline of Z. glrtyl. but it 

 diflers in having the pedicle valve more acuminate, less convex, and 



