540 CAMBRIAN BRACHIOPODA. 



Lingida loinona Hall, Sardeson, 1896, Bull. Minnesota Acad. Nat. Sci., vol. 4, No. 1, pt. 1, p. 96. (Characterizes 

 specimens from new locality. ) 



lAngulella winona (Hall), Schucheut, 1897, Bull. U. S. Geol. Survey No. 87, p. 258. (Merely changes generic refer- 

 ence.) 

 The original description by Hall follows : 



Shell small, subquadrilateral, the front nearly straight; sides nearly straight and parallel; apex obtuse, the 

 cardinal margins sloping at an angle of 80 degrees. Surface marked by fine concentric strise. 



A cast of part of a ventral valve from Osceola, Wisconsin, that appears to belong to 

 tliis species, shows the visceral area and the main vascular sinuses (PL XVIII, fig. 3). This 

 shell is more convex and has a more rounded outline than the type shell, but I tliink that this 

 is owing to the fact that the type shells are pressed flat in the sandy shales and to a degree 

 distorted. Flattened shells at Osceola are much more quadrate in outline. 



The species has been found at a number of localities, but very little more can be added to 

 the original description. The shell, although very smaU, is built up of two or more layers that 

 are lamellose toward the front of the shell. The outlines of the two valves when compressed 

 are shown by Plate XVIII, figures 3 a and 3b. 



The nearest form to Lingulella winona is L. mosia (Hall) of the Upper Cambrian. It 

 differs in the uniformly smaller size and its regular subquadrate outline. 

 The specific name is derived from Winona, Minnesota. 

 Formation and locality.— Upper Cambrian: (78 and 78c) "St. Croix sandstone," quarry near St. Croix River in 

 subm-bs of Osceola, Polk County; (85x) upper beds of the "St. Croix sandstone" near Mazomanie, Dane County; 

 (lOv) shaly beds in the "St. Croix sandstone," at Fox Glen, 8 miles (12.8 km.) east of Baraboo, Baraboo quadrangle 

 (IT. S. Geol. Survey), Sauk County; (79) "St. Croix sandstone" in bluff near Hudson, St. Croix County; and (85s) 

 "St. Croix sandstone" at Prairie du Sac, Sauk County; all in Wisconsin, i- 



(113) "St. Croix sandstone" at La Grange Mountain (or Barn Bluff), near Red Wing, Goodhue County, Minnesota. 

 (341) Near Lansing, Allamakee County, Iowa. y^ 



Lingulella winona convexa (Walcott). 



t 



Plate XVIII, figures 4, 4a-d. 



Oholus {Lingulella) winona convexus Walcott, 1901, Proc. U. S. Nat. Mus., vol. 23, p. 691. (Discussed as below as a 



new variety.) 



A small relatively convex shell occurs abundantly in the brown sandstones at Osceola 

 that appears to be an intermediate form between Lingulella winona (HaU) and L. mosia (Hall). 

 It differs from L. mosia in being a shorter shell, and from L. winona in the more regularly ovate 

 to semicircular dorsal valve and more acuminate ventral valve. 



Ohservations. — The group of shells represented by L. winona, L. mosia, and their varieties 

 appears to range from the Middle Cambrian beds of Hudson, Wisconsin, up and into the Upper 

 Cambrian beds of Osceola, Wisconsin. There is so much variety of form owing to the condi- 

 tions of preservation that it is very difficult to be always sure of the correctness of the specific 

 reference. The variety convexa may be only the uncompressed form of L. winona, which is 

 usually flattened in the shaly sandstones, or it may be a distmct species. From the material 

 available for comparison this can not be clearly determined. 



Formation and locality. — tTpper Cambrian: (78, 78s, and 78c) o "St. Croix sandstone" in quamj near St. Croix 

 River in mburbs of Osceola, Polk County; (79) "St. Croix sandstone" in bluff near Hudson, St. Croix County; 

 (85xand S85x) upper beds of the "St. Croix sandstone," near Mazomanie, Dane County; (100) "St. Croix sandstone" 

 near Menomonie, Dunn County; (79a) "St. Croix sandstone" in quarry and ledge, 0.5 mile (0.8 km.) southeast of 

 the county courthouse, Menomonie, Dunn County; (80) "St. Croix sandstone" 0.66 mile (1.1 km.) southwest of 

 the railway depot, Menomonie, Dunn County; (85s) "St. Croix sandstone" at Prairie du Sac, Sauk County; and 

 (135) "St. Croix sandstone" near Trempealeau, Trempealeau County; all in Wisconsin. 



(75) "Tonto " sandstone, near the water's edge at the mouth of Kanab Canyon, where it enters the Grand Canyon 

 of the Colorado, Arizona. 



a 78 is the type localitj'. 



