586 CAMBRIAN BRACHIOPODA. 



appear to be identical. The dorsal valve is elongate oval in outline, resembling the same valve 

 in LinguUlla atava (Matthew). 



Formation and locality. — Middle Cambrian: (344f [Matthew, 1903, p. 72']) Shales of the Coldhrooh terrane of 

 Matthew, on Dugald Brooh, Indian River; and (344e [Matthew, 1303, p. 7S]) shales of Division Eld of Matthew's [1903, 

 pp. 28 and 29] Etcheminian, on Boundary Brook, eastern side of the Escasonie Indian Keservation; both in eastern 

 Cape Breton, Nova Scotia. 



, / LiNGULELLA TEIPAEILIS (Mattliew) . 



Text figures 44a-l, page 537; Plate XLV, figures 2, 2a-f. 



Obolus triparilis Matthew, 1902, Trans. Roy. Soc. Canada, 2d ser., vol. 8, sec. 4, No. 3, p. 94, PL I, figs. 2a-c. (Dis- 

 cussed as a new species.) 

 Obolus discus Matthew, 1902, idem, p. 94, PL I, figs. 3a-d. (Mentioned as a new species.) 

 Lingulella longovalis Matthew, 1903, Geol. Survey Canada, Kept. Cambrian Rocks Cape Breton, pp. 123-125, PL VII, 



figs. 3a-f. (Described and discussed as a new species. Figs. 3b and 3d are represented in outline by text figs. 



44h and 44h', respectively, p. 537, of this monograph.) 

 Obolus (Eoobolus) triparilis Matthew, 1903, idem, pp. 136-137, PL VIII, figs. 4a-c; PL IX, figs. la-b. 



(Described and discussed as a new species. PL VIII, figs. 4a-c, is copied from Matthew, 1902b, PL I, figs. 



2a-c; PL VIII, fig. 4a, and PL IX, fig. la, are represented in outline by figs. 44b and 44b', respectively, p. 537, 



of this monograph.) 

 Obolus {Eoobolus) discus Matthew, 1903, idem, pp. 138-139, PL VIII, figs. 3a-d. (Described and discussed as a new 



species. Figs. 3a-d are copied from Matthew, 1902b, PL I, figs. 3a-d; figs. 3aand 3c are represented in outline by 



figs. 44a and 44a', respectively, p. 537, of this monograph.) 



This species is distinguished from Lingulella (Lingulepis) gregwa CMatthew) by its outUne. 

 The range of variation in its form covers both the types of the species and the types of " Lin- 

 gulella longovalis" Matthew and "Oholus (Eooholus) discus" Matthew. Matthew assigns specific 

 value to variations in length and breadth of the visceral areas of the valves. I do not find 

 that this holds good, as the shells from the same layer of rocks and not distinguishable by 

 other characters vary in the length of the visceral area of the dorsal valve from a point back 

 of the center to nearly the front of the valve. There is also considerable variation in the 

 ventral valve. On the same shell there is a variation of the surface characters from the 

 nearly plain, concentric strise to undulating strias, with minute points on the crest. This is 

 also true of the surface of Lingulella (Lingulepis) gregwa (Matthew). 



The "central" scar in the dorsal valve, mentioned by Matthew [1903, p. 136] as charac- 

 terizing "Obolus (Eooholus) triparilis," is at the bifurcation of the median ridge, and appears 

 to be a shght dej^ressiou just in advance of the bifurcation and not a true muscle scar. The 

 variation in outhne of the valves is shown in figures 44a-l. 



No specimens among the tj^pes sent by ilatthew nor in our material show areas like those 

 represented by figures 44b' and 44h'. The area is not preserved on the dorsal valves of L. 

 triparilis sent hj Matthew, and the area of the dorsal valve of his "L. longovalis" does not 

 extend so far down the lateral slopes of the shell as represented in the figure. 



The variation in the length and strength of the visceral area in the two valves is also 

 outlined from specimens showing their position. Among the specimens from the same layer 

 of rock there is a transition in form from Lingulella triparilis to Lingulella (Lingulepis) longi^ 

 nervis (Matthew) of a somewhat later stratigraphic horizon. Tliis is illustrated in figures 44f-k. 



The surface characters are of the same type in Lingulella (Lingulepis) gregwa (Matthew), 

 L. (L.) longinervis (Matthew), and Lingulella triparilis. 



"Oholus (Eooholus) discus" Matthew appears to be based on imperfect specimens of the 

 short, broad form of L. triparilis. With the types of "0. (E.) discus," L. triparilis, and 

 " L. longovalis" before me, I am not able to discover differences of specific value between them. 

 All have the same surface characters, and the gradations in form unite them into one species. 



Formation and locality. — Middle Cambrian: (13t' and 13t)a Sandstones at the base of Division Elb; (344g) 

 [Matthew, 1903, p. 77]) shales of Division Elc; (13t") sandstones of Divisions Elc and Eld; (344h [Matthew, 1903, 



a 13t is the type locality, though the specimens ua the United States National Museum collections to which that number was assigned were 

 collected later than Ilatthew's type specimens. 



