22 PROCEEDINGS OF THE >iATIONAL MUSEUM vol. 78 



to, and certainly not a mere mutation of, B. observator. It is a more 

 oblique carapace with the most prominent point on the ventral out- 

 hne farther behind the middle and the anterior end proportionally 

 narrower than in that species. The surface marking also is quite 

 different, consisting of fine pitting, or rather punctation, in B. ob- 

 servator, while in mutation laevis it consists of confluent granules, 

 separating rows of minute punctae, arranged in a concentric manner. 

 This type of marking characterizes B. rugulosa, and when the types 

 of this species were more closely scrutinized it was found that they 

 agreed not only in surface ornament but in shape as well. Matthew's 

 figure of B. rugulosa would never suggest such a relationship, but it 

 is a fact, nevertheless, the original of the figure being imperfect and 

 partly covered by matrix on its posterior side. The other specimens 

 of B. rugulosa in the type lot clearly prove the contention that this 

 species is the same as the "mutation" laevis. 



Occurrence. — Lower Cambrian (Upper Etcheminian, El6, Elc, E2a, 

 E2c, E3e): Dugald Brook, Cape Breton (mut. Zams = El6). 



Cat. Nos. 50514, 50515, U.S.N.M. (13c?", ISO- 



BRADORIA ROBUSTA (Matthew) 



Plate 1, Figures 1-5; Plate 2, Figures 1-4 



Aparchites (?) robustus Matthew, Trans. Royal Soc. Canada, ser. 2, vol. 4, 



sect. 4, 1898, p. 132, pi. 1, figs. 4a-c. 

 Indiana? robusta Matthew, Canadian Record Sci., vol. 8, 1902, p. 461. 

 Leperditia?? rugosa Matthew, Canadian Record Sci., vol. 8, 1902, p. 443, pi. 1, 



figs. 7a-c; Geol. Surv. Canada, Rept. Cambrian Rocks Cape Breton, 1903, 



p. 155, pi. 12, figs. 7a-c. 

 Bradorona perspicator mut. maxima Matthew, Canadian Record Sci., vol. 8, 



1902, p. 445, pi. 1, figs. 9a, 96; Geol. Surv. Canada, Rept. Cambrian Rocks 



Cape Breton, 1903, p. 157, pi. 12, figs. 9a, 96. 

 Bradorona perspicator mut. major Matthew, Canadian Record Sci., vol. 8, 1902, 



p. 446, pi. 1, figs. 10a, 106; Geol. Surv. Canada, Rept. Cambrian Rocks 



Cape Breton, 1903, p. 158, pi. 12, figs. lOo, 106. 

 Bradorona perspicator mut. magna Matthew, Canadian Record Sci., vol. 8, 1902, 



p. 446, pi. 1, figs. 11a, 116; Geol. Surv. Canada, Rept. Cambrian Rocks 



Caoe Breton, 1903, p. 158, pi. 12, figs. 11a, 116. 



Bradoria robusta, or, as Matthew called it, Aparchites and later 

 Indiana robusta, is represented by three specimens, A, B, and C, from 

 division Cl, B, Long Island, Kennebecasis River. A is a decorticated 

 cast of the interior of a left valve, B and C are imperfect molds of 

 the exterior of a left and a right valve, respectively. Though the 

 material is not in condition admitting of a positive determination of 

 the point, it is believed that A, which is regarded as the type of the 

 species, is distinct from B and C and that the latter two molds are 

 of a more elongate species, probably a form later called Indiana 

 pyriformis, which seems to be a large variety of Indiana secunda. 



