NO. 1229. CAMBRIAN BRACHIOPODA—WALCOTT. 691 



gray quartzitic sandstone containing a large number of specimens of 

 the '"'Lingula" of Siemiradzki. The shell proves to ])o a true Lin- 

 gulella. In the same piece of rock an obscure form of Oholus occurs 

 that may be a medium-sized Oholus ajwlli/ihw I take pleasure in 

 naming the Lingulella after its discoverer, Dr. Siemiradzki. 



Formation and locality. — Middle Cambrian, Quartzitic sandstone. 

 Pepper Mountains, near Sandomir on tlie Vistula, Russian Poland. 



OBOLUS (LINGULELLA) WINONA var. CONVEXUS. 



A small, relatively convex shell occurs abundantly in the Inown 

 sandstones at Osceola Mills, Wisconsin, that appears to l)e an interme- 

 diate form between O. (Z.) vnnona and 0. (Z.) mosia. It differs from 

 O. (Z.) mosia in being a shorter shell, and from O. (Z.) irinona in the 

 more regularly ovate to semicircular dorsal vah'e and more acuminate 

 ventral valve. 



Observations. — The group of shells represented by <>. (Z.) vnnona., 

 mosia., and their varieties appear to range from the Middle Cambrian 

 beds of Hudson up and into the Upper Camljrian beds of Osceola 

 Mills, etc. There is so much variety of form, owing to the different 

 conditions of preservation, that it is very difficult to always be sure of 

 the correctness of the specific reference. The variety convexus may be 

 only the uncompressed form of O. (Z.) irinona. which is usualh" flat- 

 tened in the shaly sandstones, or it may be a distinct species that from 

 the material available for comparison can not l)e clearly determined. 



Fm'mation and locality. — Upper Cambrian. St. Croix sandstone, 

 Osceola Mills, Menomonee, Prairie du Sac, Wisconsin. Middle Cam- 

 brian, Hudson, and Trempealeau, Wisconsin. 



WESTONIA. new subgenus of OBOLUS. 



Ovate, with ventral valve slightly acuminate; area of ventral valve 

 strongly defined and divided bv a relatively large pedicle groove. 

 Surface marked by concentric and radiating stria^ that are crossed 

 by transverse, semiimbricating, "ripple-embossed" lines. As far as 

 known the muscle scars and vascular markings are essentially the same 

 as in Obolus. 



• Eight species are referred to Westonia — Oholus { 11') aurora. O. ( If') 

 stoneanus., 0. (IF!) rogersi, 0. {W.f) lamellosas Barr, 0. (IT) escaso7ii 

 Matthew. 0. (W.) ella, 0. {W.) euglyj^hus^ and 0. (IF.) r/oarrensis. 

 They all have transverse, irregular, elevated lines; that in O. (W.) 

 stoneanas and 0. (11") r<Kjir^i have two or three sharp undulations 

 near the median line and in O. ( ir) aurora many short and more or 

 less irregular undulations on the entire central portion of the shell. 

 Beyond the short, central undulations, more or less wavelike, long 

 undulations extend to the sides of the valve, usually with a slight back- 

 ward curvature toward the margin. 



