OBOLID^. 379 



have grouped them under the subgenus Lingulobolus. The species referred to Oholus from the 

 Lower Cambrian include Oholus prindlei (PI. XXVII, figs. 3, 3a-e) which is intermediate in form 

 between Oholus apollinis (PI. XIV, figs. 6, 6a) and tlie type species of the genus Lingulella, 

 L. davisi (PL XXXI, figs. 6e, 6f). Oholus smithi (p. 416) is a typical form of Oholus, while Oholus 

 parvus (p. 408) is a minute form of which only the exterior is known. 



Of the 77 species and 11 varieties from the Cambrian referred in this memoir to Oholus and 

 its subgenera, 4 species occur in the Lower Cambrian, 46 species and 5 varieties in the Middle 

 Cambrian, 43 species and 7 varieties in the Upper Cambrian, and 10 species in the passage beds 

 between the Cambrian and Ordovician. From the Ordovician 23 species are deccribed. (See 

 table of species, pp. 110 and 113.) 



Acritis is represented in the Upper Cambrian of Russia by the type species. A species is 

 doubtfully referred to it from Nevada. 



Broggeria is represented by one species. This is found in tlie Upper Cambrian and the pas- 

 sage beds to the Ordovician of tire North Atlantic province of Europe and eastern North America. 



Fordinia includes species from the Middle and Upper Cambrian of Utah and Nevada. 



Linguloholus is represented by two species occurring in the Lower Ordovician rocks of New- 

 foundland and in conglomerate pebbles in Massachusetts. 



Mickwitzella is confined to one species identified from the passage beds between the Upper 

 Cambrian and the Ordovician of Russia. 



Palseoholus is represented by a single species from the Middle Cambrian of Nova Scotia. 



Schmidtia is represented in the Upper Cambrian "Oholus" sandstones of Russia by four 

 species, which form a peculiar and restricted local group. 



Westonia has its greatest development in the Middle Cambrian, where thirteen species and 

 one variety occur. Six species are known from the Upper Cambrian, one from the passage 

 beds to the Ordovician, and five in the lower portion of the Ordovician. 



Geograpliic distrihution of Oholus and suhgenera. — In Europe Oholus proper appears to be 

 limited to the type area in northwestern Russia, where it reaches its greatest development, and 

 to a few limited localities in Bohemia and Sweden. Its subgenera, especially Westonia, have a 

 wide distribution, the latter having been found in Russia, Bohemia, many localities on the 

 Scandinavian Peninsula, England, and China. 



Only one form is known from Sweden — 0. scTimalenseei (Walcott). The genus (or one of its 

 subgenera) appears to be present in the Cambrian of Argentina, and four species have been 

 described from eastern China — 0. chinensis (Walcott), 0. minimus Walcott, 0. ohscurus Walcott, 

 and 0. shansiensis Walcott. It is on the North American continent that Oholus reaches its 

 greatest development outside of its original localities in Russia. It is widely distributed and 

 often occurs in great numbers at favorable localities. It occurs along the lines of the Appa- 

 lachian Range from Newfoundland, Cape Breton, and New Brunswick to Tennessee. It is 

 represented in the northern Mississippi Valley region, in the isolated uplifts of Cambrian rocks 

 in the Black HUls of South Dakota, the Ozark Mountains of Missouri, the Llano Hills of central 

 Texas, and westward in Wyoming, Montana, Utah, and Nevada. 



Of the species m this memoir that are placed under Oholus from Bohemia, . feistmanteli 

 (Barrande) and 0. complexus Barrande are probably true representatives of the genus, but the 

 following species are exceedingly doubtful in their generic identification: 



Obolus ? advenus Barrande. 

 Obolus ? ancillus (Barrande). 

 Obolus ? bavaricus (Ban-ande). 

 Obolus ? minor Barrande. 

 Obolus ? mirandus (Barrande). 

 Obolus ? palliatus Barrande. 

 Obolus ? rokitzanensis Barrande. 



This is true also of the two forms from Sardinia: Oholus? zoppi Walcott, and O.f menegJiinii 

 Walcott. 



