PLATE XLITI. 143 
LInGULELLA (LINGULEPIS) EXIGUA (Matthew)—Continued. 
Fieure lt. Large, partly exfoliated dorsal valve, of the same type as the ventral valve represented by figure 1. 
Associated with the specimen represented by figure lq. U.S. Nat. Mus. Cat. No. 52468d. 
lu, lw, and 1x. Casts of the interior of dorsal valves showing variation in outline, form of visceral cavity, 
pitting of inner surface of valve, ete. Associated with the specimen represented by figure lq. U.S. 
Nat. Mus. Cat. Nos. 34761m, 34761lo, and 34761p, respectively. 
iv. Interior of a dorsal valve associated with the specimen represented by figure 1q, in which the pits are 
arranged like beads along the lines of growth. U.S. Nat. Mus. Cat. No. 34761n. 
ly. Part of interior of dorsal valve associated with the specimen represented by figure 1q, showing ridges 
on which the central muscle scars occur, main vascular canal ridges, and fine pitting of surface. U.S. 
Nat. Mus. Cat. No. 34761q. 
1z. Cast of interior of dorsal valve in which the visceral area extends well toward the front. Locality 11z, 
Middle Cambrian sandstone on Big Ridge, 2 miles south of Marion Bridge, Cape Breton, Nova Scotia. 
U.S. Nat. Mus. Cat. No. 51870a. 
