ABT. 4 CAMBRIAN CONCHOSTRACA — ULRICH AND BASSLER 13 



pervetus concinna, S. cambrica, and S. acuta, these agree in all essen- 

 tial respects with Bradoria. In the so-called Schmidtellae the form is 

 short and tumid, but not more so than in certain species of Bradorona 

 (as B. obesa). Except Schmidtella f pervetus concinna, in which the 

 ocular tubercle is barely distinguishable, all of the other species named 

 in this paragraph have this tubercle more or less well developed. 

 Variability in prominence of the "eye tubercle" in the Leperdi- 

 tiidae, however, is so common and has been proved to be of such 

 little consequence in the generic grouping of the species that a similar 

 inconsequence is suggested for the variation of the corresponding 

 tubercle in these Cambrian crustaceans. Indeed, as a study of 

 abundant material in Doctor Walcott's collection shows, individuals 

 even may vary considerably in the relative development of the 

 "eye tubercle." Considering species, the possibility of duplication 

 under separate generic heads was immediately suggested, and before 

 we had progressed very far in our study of the Matthew types, such 

 duplication was demonstrated. It was induced, in the cases in mind, 

 sometimes by exaggerated values ascribed to nonessential variations 

 in development, but oftener through imperfections in preservation 

 or incomplete preparation of the specimens. 



The genus Indiana is noted above as a synonym in part. But if 

 it were insisted that when no genotype is designated the first species 

 following the generic description is to be so regarded, the genus 

 could not stand. The first species, namely, Indiana ovalis, is an 

 unquestionable Bradoria, being in fact a close aUy of B. rugulosa 

 and B. robusta. In this case, however, we think it advisable to trans- 

 fer the rank of genotype to /. lippa one of two or three clearly con- 

 generic species referred to the genus when it was first described by 

 Matthew. Restricted to these and similar species, Indiana is dis- 

 tinguished by its oval, smooth form and total absence of the ocular 

 tubercle. The gap between the valves is greater, and this, together 

 with the other differences, probably indicates peculiarities of more 

 serious import than can be established now. 



All of the species of Bradoria as here revised bear a single node, 

 the ocular tubercle. This, while always close to the anterocardinal 

 angle, varies considerably in prominence. Rarely it is barely dis- 

 tinguishable, but as a rule it is a conspicuous feature, and not infre- 

 quently the definition of its base is emphasized by a narrow depres- 

 sion extending in part or entirely around it. In most of the species 

 the outhne of the valves is more or less distinctly divisible into five 

 unequal sides. The angles marldng off these sides are sometimes 

 sharp, never equally so, the ventral angle generally the least acute, 

 and in some cases all but the two defining the upper and lower ex- 

 tremities of the truncated, narrow anterior end are practically obso- 

 lete. The narrowest of the five sides is terminated above by the 



