N0.12J9. CAMBRIAX BRACHIOPODA—WALCOTT. ()73 



and the species was referred to Obolella by Mr. Billings. It differs so 

 radically from Obolella in the character of the areas of the valves and 

 the interior markings that it is scared}^ necessary to institute compari- 

 sons between them. 



01)olella as known at present is limited to six species and one variety: 



Oholdla chromaiica Billings". 

 Obolella ailant'tca "Walcott. 

 Obolella a^issa Hall. 

 Obolella crassa var. elonyata "Wak-ott. 

 . Obolella favosa Linnarsson. 

 Obolella llndstrdmi Walcott. 

 Obolella mobergi Walcott. 



Of the above two species 0. chromatica and 0. atlantiea belong to 

 the upper portion of the Olenellus fauna, and 0. crassa and var. elon- 

 (jata to the lower portion. The three Swedish species O. favosa^ O. 

 Jindstruinl, and O. inohergi are from the basal Cambrian sandstones 

 and may belong to the same horizon as 0. crassa. 



The species that have heretofore ])een referred to Obolella, in addi- 

 tion to those listed above, are noAV distributed in the following genera: 



? ambigua Walcott =Elkania. 



0. cingidata Billings =Kutorgina. 



0. circe Billings =Billingsella. 



0. coelata Billings =Acrothele. 



0. desquamata Billings = Obolella crassa. 



0. desiderata Billings =Elkania. 



0. discoidea Hall and Whitfield = Obelus (Lingulella). 



0. gemma Billings =Bicia. 



0. gemmula Matthew =:Obolns (Lingulella). 



0. ida Billings =(?) 



0. minuta Hall and Whitlield=Acrotreta. 



0. misera Billings =Linnarssonia. 



0. nana - Meek and Hayden =Dicellomus. 



0. nitida Ford =Linnarssonia (?) . 



0. pectenoides Whitlield =Dicellomus. 



0. polita Hall =Dicellomus. 



0. pretiosa Billings =Linnarssonia. 



0. prima AVhitfield =Obolus (Lingulepis). 



0. transversa Hartt =Linnarssonia. 



OBOLELLA MOBERGI, new species. 



General form ovate, with the ventral valve subacuminate and the 

 dorsal valve obtusely subacuminate; valves moderate!}' convex. Beak 

 of the ventral valve slightly elevated above the plane of the shell; 

 beak of the dorsal valve curved down to the plane of the margin. 

 Surface of the shell marked by concentric lines and stride of growth, 

 and in some examples by rather strong, radiating, broken, and slightlj^ 

 irregular raised lines. The elevated lines are of the same character as 

 those on Bicia gemma. The shell is formed of a thin outer la3'er and 

 numerous inner layers or lamellte, the latter over the anterior half of 



Proc. N. j\I. vol. xxiii 43 



