480 CAMBRIAN BRACHIOPODA. 



lines that extend from tlie apex, with a sUghtly outward curvature, to the base of the area. 

 Striae of growth cross the area parallel with its base, being much stronger on the area than in 

 the pedicle furrow. The area of the dorsal valve is fully as prominent as that of the ventral 

 valve. It curves forward at the center and extends well out on the cardinal slopes. The 

 flexure lines are clearly defined well out toward the lateral margin. The striae of growth cross 

 the area parallel to the base. 



The cast of the interior of the ventral valve shows only the outline of the visceral cavity, 

 and that the main vascular sinuses extend a considerable distance in advance of the visceral 

 cavity. The cast of the interior of the dorsal valve shows that it had a strong, broad, central 

 ridge, divided by a faint longitudinal median sinus. Only traces have been seen of the main 

 vascular sinuses. 



Observations. — This is a very pretty little species that, in the absence of well-defined speci- 

 mens, I [1901, p. 694] confused with the young of "Lingulepis gregwa" Matthew. Material 

 collected by S. Ward Loper at the type locality, however, proves that the shell differs consider- 

 ably from that of the young of Lingulella (Lingulepis) gregwa, although specimens of the dorsal 

 valve of the two forms are often very much alike. 



Matthew's illustrations [1903, PI. VI, figs. 2a-b, d-g] of Lingulella atava are somewhat 

 diagrammatic, as though they were drawn to represent the average form of several specimens. 

 With the type specimens before me I find considerable variation in width and outline. Some 

 have the outlme of Lingulella collicia (Matthew) and the two types of the latter species are 

 much like Matthew's figures of Lingulella atava [1903, PI. VI, figs. 2a-b, d-g]. The specimens 

 of Lingulella collicia have the rotund, subquadrate outline of Lingulella atava and not the uniform 

 curvature of Matthew's figures of Lingulella collicia [1903, PI. VI, figs. 3a, 3b]. With a large 

 series of well-preserved material from the type locality and formation, I have endeavored to 

 represent two forms that may be referred to Lingulella atava and Lingulella collicia, respectively. 

 Lingulella atava is more slender and its sides are more uniformly curved than L. collicia, and it 

 is also usually larger. Lingulella cania (Walcott) is a narrow, elongate form. 



Formation and locality. — Middle Cambrian: (lOp) Sandstones just below the waterfall in Division E2b; (13d 

 and 13d') sandstones opposite the third waterfall, between Divisions E2a and E2b; (131') sandstones of Division 

 E3a; (344) sandy shales of Division E3b; (13n" and 344b) sandstones of Division E3d; (13n') o sandstones of Division 

 E3e; and (13nand 344d) sandstones of Division E3f; all in Matthew's [1903, p. 21] Etcheminian, on Dugald Brook, 

 Indian River, eastern Cape Breton, Nova Scotia, Canada. 



Lingulella atava iNSLiLiE (Matthew). 



Plate XXXV, figures 8, 8a. 



Leptobolus atavus insulm Matthew, 1903, Geol. Survey Canada, Kept. Cambrian Rocks Cape Breton, pp. 110-112, 

 PI. VI, figs. 4a-c. (Described and discussed as a new variety. The specimens represented by figs. 4a and 4b 

 are redrawn in this monograph, PI. XXXV, figs. 8 and 8a, respectively.) 



The form of this shell is much like that of Lingulella cania (Walcott) or a narrow L. atava 

 (Matthew). The material representing it is not well preserved. Matthew [1903, PI. VI, figs. 

 4a-c] has illustrated it with three somewhat diagrammatic figures that give his conception of 

 its form and interior markings. I have figured two of the best preserved of the typical 

 specimens. They show the general form and character to be similar to those of L. atava. 



Formation and locality. — Middle Cambrian: (307d [Matthew, 1903, p. 110]) Sandstones believed to belong to 

 Division E2a of Matthew's Etcheminian, at Youngs (McFees) Point, George River, eastern Cape Breton, Nova Scotia. 



I Lingulella axjga (Walcott). 



Plate XXIV, figures 6, 6a-g. , 



Obolus {Lingulella) auga Walcott, 1898, Proc. U. S. Nat. Mus., vol. 21, pp. 396-397. (Described as below as a new 

 species.) 



General form svibcuneate, with ventral valve obtusely acuminate, and the dorsal valve 

 rounded acuminate; valves moderately convex. Surface of the shell, as indicated by casts 



a ISn' is the type locality, though the specimens in the United States National Museum collections to which that number is assigned were 

 collected later than the type specimens. Localities 344, 344b, and 344d are cited by Matthew (see pp. 2G8-269). 



