NO. 1152. CAMBRIAN BRACniOPODA—WALCOTT. 397 



ill a few speciinena, and in one specimen the anterior lateral muscle 

 scars appear to be present. 



Observations. — In {lie form of the valves this species is somewhat 

 similar to 0. ( L.) f/rawlis; otherwise it appears to be quite distinct from 

 any other described species. 



Formation and locality.— Middle Cambrian, sandy layers of the Rome 

 formation, at Shooks Gap in Bays Mountain, 10 miles east of Knoxville, 

 Tennessee. 



Type.—:^o. 27306, U.S.KM. 



OBOLUS (LINGULELLA) BELLUS, new species. 



General form ovate, with ventral valve obtusely acuminate; dorsal 

 valve broad ovate; valves moderately convex, as far as can be deter- 

 mined from the somewhat compressed specimens as they occur in the 

 sandy shales. 



Surface of shell with numerous concentric lines of growth, witli 

 exceedingly fine, slightly irregular stria' on the interspaces between the 

 stronger concentric lines. Owing to the roughened surface formed by 

 the tine striu', the outer layer of the shell adheres to the arenaceous 

 matrix, leaving the shiny inner layer on tlie shell. This is marked by 

 concentric and numerous fine radiating strife. 



The shell is apparently thin, and formed of a very thin outer layer, 

 with one or more thin inner layers or lamelhe. The casts of the inte- 

 rior surface of the ventral valve show numerous papilla' arranged in 

 concentric lines on the posterior half of the shell. These correspond 

 to the puucta? of the inner surface. 



A large ventral valve has a length of 15 mm.; width, 9 mm.; and a 

 dorsal valve 13 mm. in lengtli has a width of 10 mm. The specimens 

 111 the collection average from 2 to 3 mm. smaller than this. 



The cast of the area of the ventral valve shows that it was rather 

 long and extended well out onto the cardinal slope; it is divided mid- 

 way by a strong iiedicle furrow, and toward the lateral margin by a 

 narrow iiexure line. The area is marked by tine strite of growth par- 

 allel to the margin. The area of the dorsal valve is rather short, but 

 it extends laterally well out on the cardinal sloi)es. The shallow curve 

 corresponding to the pedicle groove of the larger valve is wide and 

 clearly defined. 



The casts of the interior of the valves show almost no traces of the 

 vascular markings or muscle scars. Only the anterior lateral muscle 

 scars have been observed in the ventral valve. 



Observations. — This fine species occurs in great abundance in the 

 upper beds of Little Bell Island associated with 0. {L.) bellnlus, and 

 also in the higher beds on Great Bell Island, a little below the layers 

 carrying Liyujulobolus affinis and Sphwrobolus spissus. Although found 

 at some little distance above the horizon in which I collected a species 

 of Olenus, I refer the horizon to the Uj)per Cambrian. 



