CAMBRIAN BRACHIOPODA — WALCOTT O3 



valve ; the position of the transmedian and anterior-lateral muscle 

 scars is indicated about half way between the main vascular sinuses 

 and the postero-lateral margin of the valve. 



Observations. — This species is characterized by its finely granular 

 surface, short cardinal area, and relatively thick shell. It has the 

 general form of Ohohis Imnhorni (Meek) [1871, p. 185] and Oholus 

 zi'illisi (Waleott) [1898&, p. 418]. It differs from both of these 

 species in having a granulated surface and shorter" cardinal area. It 

 is a Lower Cambrian form, but appears to be represented in the 

 ^Middle Cambrian by Ohohis willisi and in the Upper Cambrian by 

 Obohis laiiibonii. The associated fossils are Wimanella shelbyensis 

 (see p. 100), Micromitra (Paterina) major (Waleott) [1905, p. 

 304], Micromitra (Paterina) zvilliardi (see p. 60), and numerous 

 fragments of two or three species of Olenellns. 



The specific name is given in honor of Prof. E. A. Smith, State 

 Geologist of Alabama. 



Formation and Locality. — Lower Cambrian : ^lontevallo shale 

 (i) 4 miles (6.44 km.) south of Helena; and (2) along road just 

 north of Buck Creek, .12^ mile {.20 km.) northeast of Helena; both 

 in Shelby County, Alabama. 



OBOLUS TETONENSIS LEDA, new variety 



This is the Upper Cambrian representative of O bolus tetonensis 

 Waleott [1901, p. 684] of the Middle Cambrian of the Teton ]\Ioun- 

 tains. Stratigraphically it occurs over 2,000 feet (609.6 m.) higher 

 in the Cambrian section of the House Range, and the localities are 

 400 miles (644 km.) apart. The variety leda differs from the species 

 in having more numerous, fine, thread-like striae and in the fact that 

 the ventral valve is usually more obtuse in old shells. 



Formation and Locality. — Upper Cambrian : 1.945 to 1,975 ^^et 

 (592.8 to 601.9 m.) above the Middle Cambrian and 1,340 to 1,370 

 feet (408.4 to 417.6 m.) below the top of the Upper Cambrian, in the 

 siliceous limestones of the Notch Peak formation [Waleott, 1908a, 

 p. 9], on the slopes of Notch Peak, 5 miles (8.05 km.) southwest of 

 ]^Iarjum Pass, House Range, Millard County, Utah. 



OBOLUS WORTHENI, new species 



Plate 7, Figure 17 

 General form subcircular, with the ventral valve very obtusely acu- 

 minate and the dorsal valve slightly transverse, both valves slightly 

 convex ; ventral valve with the beak at the posterior margin, which 

 rises slightly from the general plane of the margin of the valve ; the 

 minute beak of the dorsal valve is at the posterior margin. 



