NO. 1152. CAMBRIAN BBACHIOPODA—WALCOTT. 415 



a large linguloid brachiopod, which appears to be identical with Obolus 

 {Ungulobolus) affinis Billin.ys, from the Lower Ordovician rocks of 

 Newfoundland. The material is somewhat imperfect, but 1 do not 

 know of any other large brachiopod of this type from tlie Cambrian 

 or Ordovician rocks. 



On Great Bell Island, Newfoundland, 0. (X.) rogersi is associated 

 with 0. {L.) bellus and 0. {Lmfjulobohis) affinis. 



Formation and localitij. — Lower Ordovician, cifuartzitic pebbles in 

 the Carboniferous conglomerates about Narragausetb Bay, Rhode 

 Island, and in the drift along the beaches of the coast of lihode Island, 

 and also of Marthas Vineyard, Massachusetts, and probably also at 

 other points where the i)ebbles may have been carried by the glacial 

 drift. Great Bell Island, (Conception l>ay, Newfoundland. 



T//i)e.— No. 27336, U.S.N.M. 



OBOLUS (LINGULELLA) ROTUNDATUS, new species. 



This small species is associated with O. [L.) manticulu.s. It differs 

 from it in its nearly circular form and more strongly y)itted or jiunctate 

 interior of the valves. A cast of the interior of a dorsal valve shows 

 a well defined area, the cast of the median ridge and septum, and the 

 central muscle scars. The ventral valve has a length of 3.5 mrn.; 

 width, 3 mm. Dorsal valve, length, 3 mm.; width, 3 mm. 



Formation and locality. — Upper Cambrian, and in the lower beds of 

 the Ordovician. The type specimens from the Lower Ordovician are 

 fiom Schellbourne, Schell Creek Range, Nevada; and the Montana 

 specimens from a point west of Bear Creek, south of Gallatin Valley. 



Types.— :^ OS. 27337-8, U.S.N.M. 



OBOLUS (LINGULELLA) SIMILIS, new species. 



Shell small, general form ovate, with the ventral valve subacumi- 

 nate, and the dorsal valve rounded-ovate in outline. There is some 

 variation in the outline of the valves. Surface of the shell marked 

 by concentric lines of growth and very line, slightly irregular, con- 

 centric striai; where the outer surface is well preserved fine radiat- 

 ing striic may be seen with a strong magnifying glass. When the 

 outer layer of the shell is exfoliated the outer surface of the inner 

 layer is marked by tine concentric lines and very fine numerous radiat- 

 ing stria'; the inner surface of the shell shows concentric lines of 

 growth, and faint, scattered pits or puncta'. The shell is of medium 

 thickness, and formed of a thin outer layer, with one or more inner 

 layers or lamelhe; the latter are especially prominent toward the 

 front, where they have essentially the same arrangement as in O. (L.) 

 acutangulufi. The average length of tlie ventral valve is from 4 to 5 

 mm.; width, 2.5 mm. An associated dorsal valve 4 mm. in length 

 had a width of 3 mm. 



