SCHUCHERTINID^. 585 



FamUy SCHUCHERTINID^E Walcott. 



Genus SCHtTCHEBTINA Walcott. 



Schuehertina Walcott, 1905, Proc. U. S. Nat. Miis., vol. 28, p. 323. (Mentioned as beiow as a new genus.) 

 Scliuchertina Walcott, 1908, Smithsonian Misc. Coll., vol. 53, No. 4, PL XI, and pp. 142 and 145. (Classification of 

 genus.) 



The description of the type species includes that of the genus, as but one species is known. 

 Type. — Scliuchertina cambria Walcott. 



The genei'ic name is given in recognition of the thoi'ough work that Prof. Charles Schuchert 

 has done on the Brachiopoda. 



, SCHUCHEETINA CAMBRIA Walcott. 



Plate LI, figures 6, 6a-m. 



Schuehertina cambria Walcott, 1905, Proc. U. S. Nat. Mus., vol. 28, pp. 323-324. (Described and discussed as below 

 as a new species.) 



Shell subovate, with valves obtusely acuminate, biconvex. Surface marked by concentric 

 lines and strise of growth and fine radiating strise. The inner and outer surface of the shells 

 have very fine punctse, but no traces of punctse penetrating through the shell have been 

 observed. 



The largest ventral valve dias a length of 22 mm.; width, 23 mm.; dorsal valve, length, 

 17 mm.; width, 18 mm. Shell substance calcareous, rather thick on the umbonal region and 

 thin toward the margins. 



Ventral valve subacuminate, moderately convex; on some of the larger shells a broad mesial 

 fold and arching of the frontal margins are present; apex terminates at the margin above a 

 triangular opening or delthj^rium; area small and within the plane of the margins of the valve; 

 it is attached to the bottom of the valve and divided midway by a very slight pedicle groove; the 

 margins of the delthyrium-like opening sustain an angle of about 45° to the plane of the valve, 

 and the solid area within is at its center nearly on the plane of the valve; the anterior margins 

 of the area extend upward to meet the margins of the shell, thus forming a solid arched area. 

 The interior of the valve is marked by radiating, shallow, narrow furrows that vary in number 

 and strength in different shells; just in front of the area on each side of the median line oval 

 depressions occur, which correspond in position and shape to the diductor muscle scars of the 

 ventral valve of the Billingsellidse, and they are so interpreted on the figures ; traces of the adduc- 

 tor scars are found on each side of the median line. Dorsal valve obtusely acuminate, about as 

 convex as the ventral valve; apex marginal on the broad, low, median arch of the posterior 

 margin; the only trace of an area that has been observed is shown on figure 6j; a broad, 

 shallow mesial sinus and projecting front margin occur on adult shells; the position of the 

 anterior and posterior adductor muscle scars is indicated, also the umbonal thickening in 

 which the diductor muscles were probably attached, as there is no trace of a cardinal process; 

 radiating furrows like those in the ventral valve are strongly marked in adult shells. 



Observations. — Scliuchertina cambria is a shell that, as far as I know, is unique. In its 

 exterior form it suggests a biconvex orthoid genus, and this likeness is further increased by the 

 flabelliform scars of the ventral valve; the smooth surface and solid cardinal areas suggest 

 Elkania. It may be that Schuehertina is a type derived from some early Cambrian form allied 

 to the Billingsellidse. Its general aspects appear to affiliate it with the Orthidse. 



Formation and locality. — Middle Cambrian: (5k) Limestone in Meagher County on the road to Wolsey, about 

 1 mile (1.6 km.) south of the divide at the head of Sawmill Creek, and 8 miles (12.8 km.) south of Neihart, Little Belt 

 Mountains quadrangle (U. S. Geol. Sui-vey), Cascade County, Montana. 



