AET. 4 CAMBRIAN CONCHOSTRACA — ULRICH AND BASSLER 15 



Bradorona ohservator mut. ligata Matthew (part), Canadian Record Sci., vol. 8. 

 1902, p. 451, pi. 1, fig. 17; Geol. Surv. Canada Rept. Cambrian Rocks Cape 

 Breton, 1903, p. 162, pi. 12, fig. 17. 



The type lot of this species, the genotype, contains three speci- 

 mens, A, B, and C.^ The one marked A is mostly a cast of the inte- 

 rior of Bradoria benepunda, both the outline and contour of the valve 

 and the punctations of a small patch of remaining shell agreeing 

 with that species. B and C are evidently conspecific, and C is the 

 specimen used by Matthew in illustrating the species. Matthew's 

 figure of the left valve of this specimen (pi. 1, fig. 11) gives a false 

 impression of the true outline, the ventral portion of the specimen 

 being somewhat obscured by matrix and the whole carapace crushed 

 so as to straighten this side a trifle and to expose the cardinal edge 

 of the opposite right valve. The true outline of the valves — at any 

 rate of the right, should the two, as seems highly improbable, be 

 unequal — is more nearly approximated by specimen B. This indi- 

 cates that the posterior half is proportionately wider than it is rep- 

 resented in Matthew's figure. 



The characteristics of the species, as indicated by this specimen 

 are (1) the rather uniform rounding of the posterior end, (2) the com- 

 parative obsolescence of the postcardinal and postventral angles, (3) 

 the far anterior location of the ocular tubercle, and (4) the relatively 

 coarse pattern of its surface punctation, but an excellently preserved 

 example in the Walcott collections from the type locaUty show^s that 

 the posterior outline is sharply rounded in the postventral part and 

 appreciably angulated in both the anteroventral and the postdorsal 

 parts. On the whole, then, the outline of B. scrutator is somewhat 

 obscurely quadrangular, thus agreeing better with the other species 

 of its section of the genus. 



Bradorona ohservator ligata Matthew is regarded as a synonym of 

 Bradoria scrutator. The collection contains two specimens of this 

 "mutation," both imperfect. They are quite distinct, one (A) 

 being the same as the types of B. scrutator, the other (B) being a more 

 triangular carapace and marked by exceedingly fine punctae (much 

 finer than in B. scrutator). Neither is closely related to the typical 

 form of B. ohservator. The specimen A is evidently the original of 

 Matthew's Figure 17 and is accepted as the true type. This con- 

 clusion is fortified by the fact that this specimen alone fits the de- 

 scription in having "punctation rather coarse." This specimen is a 

 trifle wider in the direction of the vertical diameter than usual in 

 typical examples of B. scrutator, but this difference is certainly not of 

 specific, and, in our opinion, not even of varietal, importance. The 



• The Matthew types have been carefully lettered when a species is represented by more than one speci- 

 men. In such cases, Doctor Matthew probably used all the specimens in formulating his descriptions. 

 It will be noted that in the present work we have found it necessary to restrict his types to the figured 

 specimens in practically all cases. 



