308 PROCEEDINGS OF THE NATIONAL MUSEUM. 



This species appears to be clearly distinct from any described form. 

 It may be compared with O. {L.) davini in relation to its size, but not 

 in other respects, except that it has something of the same general 

 outline. 



Formation and locality. — Upper Cambrian, arenaceous shales of th(! 

 upper beds on Little Bell Island and Great liell Island, Conception 

 Bay, Newfoundland. 



Tyjies.—Nos. 27;i07-8, U.S.N.M. 



OBOLUS (LINGULELLA) BELLULUS, new species. 



General form ovate, with the ventral valve obtusely acuminate, and 

 the dorsal valve round ovate. Valves moderately convex. Surface of 

 shell marked by concentric lines of growth and exceedingly line, irreg- 

 ular striiii, that give the same appearance to the surface as that seen 

 on 0. (/>.) ella, O. (L.) daicsoni, 0. {L.)fra(/ilis, and on a larger scale on 

 O. [L.) radulus. The outer layer of the shell usually adheres to the 

 arenaceous matrix, leaving the shiny inner layer of the shell. This is 

 marked by concentric striie and lines of growth, and tine radiating 

 striiie. The shell is tliin and formed of a very thin outer layer, and 

 one or more thin inner layers or lamella'. 



The average length of the ventral valve is from 4 to 5 mm.; width, 

 3 to 3.5 mm. The dorsal valves are a little shorter, 0.5 mm. to 1 mm. 



The cast of the area of the ventral valve shows it to be elongate, 

 divided midway by a narrow but strong pedicle furrow and about 

 midway between the pedicle furrow and the lateral margin by a nar- 

 row flexure line; it is marked by stria' of growth parallel to its base. 

 The area of the dorsal valve is not well shown by the specimens in the 

 collection. 



The casts of the interior of the ventral valve show somewhat 

 imperfectly the visceral cavity, but not the muscle S(;ars. In an inte- 

 rior of the dorsal valve the main vascular sinuses are well shown, also 

 the median septum. The central muscle scars are faintly shown in one 

 fragmentary interior of the dorsal valve. 



Observations. — This beautiful little species occurs in the arenaceous 

 shales and thin bedded sandstones of Little Bell Island in association 

 with the larger species 0. {L.) bellus. It is closely related to 0. {L.) 

 daicsoni, but differs somewhat in form and the more anterior position 

 of the visceral cavity in the dorsal valve. The si)ecies is the Upper 

 Cambrian represeutativeof the Middle Cambrian species 0. {L.) daicsoni. 

 It occurs at about the same horizon as O. (L.) hilliiifislana, but difl'crs 

 decidedly from it in form and convexity, the only points of comparison 

 the material permits of being made. 



Formation and locality. — Upper Cambrian, arenaceous shales about 

 75 feet down in the section of Little Bell Island, Conception Bay, 

 Newfoundland. 



Tyjjc— No. 27309, U.S.N.M. 



