ART. 4 CAMBRIAN CONCHOSTRACA — ULRICH AND BASSLER 69 



with a good species of Bradoria in the collections of the National 

 Museum from the same locality. Being distinct, the specific name is 

 retained and the species accordingly has been described on a preceding 

 page under the name Bradoria ovalis. 



As detailed on a former page, still another of the species referred to 

 Indiana by Matthew iti 1902 belongs to Bradoria., namely, the form 

 described hj him in 1898 as A'parchites? robustus. The synonymy of 

 this species is very complicated, the study of Matthew's collection 

 of original t,ypes having show^n that he gave no less than five names, 

 distributed among three genera, to different individuals of one and the 

 same species. 



The hitherto accepted genotype of Indiana being an unqualified 

 Bradoria, the former genus must either fall into synonymy under the 

 latter, or be restored to good standing by the selection of another 

 genotype. The latter course is thought the more advisable, because 

 the genus, as constituted by Matthew, includes a distinguishable 

 group of species, the essential characters of which are brought out 

 in the above revised definition of Indiana. Of the other species 

 originally referred to the genus by Matthew, /. lippa and /. pyri- 

 formis are perhaps equally characterisric of the revised genus. The 

 type specimen of the former being rather better preserved than the 

 other, it is selected as the genotype. 



Based on /. lippa and /. pyrijormis, both of Matthev^', and includ- 

 ing the congeneric Aparchites secunda Matthew, Leperditia derma- 

 toides Walcott, L. primaera Matthew, Primitia acadica Matthew, 

 Aparchites anderssoni Wiman, and the new species of the present 

 work, /. longula, I. suberecta, I matthewi, I. labiosa, I.Jaba, I. curia, 

 and /. impressa, the genus Indiana is distinguished from Bradoria by 

 the entire absence of ocular and other tubercles. Other differences 

 are found in the greater gap in the ends and ventral parts of the cara- 

 pace, and in the shght inequaUty of the dorsal parts of the valves, 

 the margin of the left valve in at least some of the species, extending 

 over the median Une of the back so as to overhang the gaps. Again, 

 in most of the species of Indiana, the outUne of the valves has a retral 

 swing that is quite foreign to the average Bradoria. Further, it is to 

 be noted that the angulation of the posterior and anterior parts of 

 the outline frequently seen in species of Bradoria is either entirely 

 absent or barely distinguishable in Indiana. Finally, the surface of 

 the species to which it is proposed to restrict Indiana has, despite its 

 fine punctation, a pohsh that is never observed in Bradoria. 



On account of the usual imperfections resulting from crushing, 

 folding, and breakage of the carapaces prior to fossihzation, it is 

 likely that some difficulty may be experienced in distinguishing certain 

 forms from species belonging to the new genus Mononotella, founded 

 on the species originally described by Matthew as Primitia? Jusifor- 



