ART. 4 CAMBKIAN CONCHOSTRACA — ULRICH AND BASSLER 25 



Bradorona observator Matthew, s. s. Canadian Record Sci., vol. 8, 1902, p. 448, 

 pi. 1, figs. 15a-15c; Geol. Surv. Canada, Rept. Cambrian Rocks Cape 

 Breton, 1903, p. 160, pi. 12, figs. 15a-15c. 



There are four specimens marked as types of Bradorona perspicaior 

 all doubtless conspecific. One, marked "A," the origmal of Mat- 

 thew's figures 8a, 86, and 8c, is the best preserved and therefore 

 considered as the real type of the species. The original figures are 

 accurate except in representing the ventral outline more sharply 

 rounded than it is in the specimen and in giving the valve greater 

 thickness (one-third more) in the edge views than we think it possesses. 

 The ocular tubercle also is rather nearer the hinge than shown in the 

 figure. Bradorona observator, s. s., is regarded as conspecific, and 

 B. spectator a closely allied species, differing chiefly in having a some- 

 what coarser surface network. 



In the Matthew's collection, seven specimens are called types of 

 Bradorona observator. All of these seem to be merely young examples 

 of Bradoria perspicator, and it is important to note that the types of 

 the two so-called species are all from the same locahty and bed 

 (Lower Etcheminian, ElD, Boundary Brook, Nova Scotia). The 

 surface pitting is fine and the same in both sets of types, and the out- 

 line and contour of valves precisely the same except that in the 

 smaller examples {B. observator s. s.) the postcardinal angle or spine 

 is less developed than in the larger examples {B. perspicator s. s.). 

 It is a singular fact that the types of the three species, spectator, 

 perspicator, and observator, are much nearer each other than any of the 

 three is to the so-called mutations of the last. 



Matthew's figure of B. observator (hke that of B. perspicator) is too 

 narrowly rounded at the middle of the ventral edge; i. e., this part 

 of the outline is more produced in the illustration than in the original. 



Occurrence. — Lower Cambrian (Lower Etcheminian, division Elc?, 

 E2a, E26): Boundary Brook, Escasonie, Cape Breton. Walcott 

 locality lOp, ISd", Dugald Brook, Nova Scotia. 



Plesiotype.— Cat. No. 50532, U.S.N.M. (13c?'0- 



BRADORIA SPECTATOR (Matthew) s. s. 



Plate 1, Figure 19 



Bradorona spectator Matthew, Canadian Rec. Sci., vol. 8, 1902, p. 447, pl.l, figs. 

 12a-d; Geol. Surv. Canada, Rep. Cambrian Rocks, Cape Breton, 1903, p. 

 158, pi. 12, figs. 12a-d. 



The types of this form indicate such close relations to B. perspicator 

 s. s. that we feel justified in doubting they can be successfully distin- 

 guished as species. Both forms are Lower Etcheminian and found at 

 the same localitj'', namely, Boundarj^ Brook. The selected types of 

 the two differ slightly in size of surface punctation and a httle in 

 shape, B. spectator being somewhat less triangular and proportionately 



