ART. 4 CAMBRIAN CONCHOSTRACA — ULRICH AND BASSLER 83 



in other forms may serve as a satisfactory Clue. This is a slightly 

 depressed, very minutely granular circular spot, situated near the 

 middle of the valve. This probably represents the external aspect 

 of a muscle spot corresponding to a similarly located smooth spot 

 observed in internal casts of /. primaeva (?Matthew) Ulrich and 

 Bassler and Bradoria steadi (Matthew). 



Occurrence. — Middle Cambrian (Acadian, division Clcl), Porter's- 

 Brook, St. Martins, New Brunswick. 



INDIANA? MINIMA Wiraan 



Plate 9, Figure 14 



Indianaf viinima Wiman, Bull. Geol. Inst. Upsala, vol. G, pt. 1, 1902, p. 48, 

 pi. 1, figs. 38, 39. ife^*'.'- 



Wiman's figures of this doubtful species are reproduced on Plate 9. 

 Judging solely from these figures and the original description, it seems 

 highly improbable that the species really belongs to Indiana, or indeed 

 to any established genus of Cambrian bivalved Crustacea. Its small 

 size and elliptical form suggests Ostracoda like Cytherella and Bytho- 

 cypi'is, but the fact that its shell is "chitinous, black and poUshed," 

 probably precludes all likelihood of genetic relationship to such later 

 Crustacea. In the character of its test it appears to agree with the 

 majority of the Cambrian bivalves treated in this work. Though 

 Indiana affords perhaps as good a temporary lodgment for the species 

 as any known genus, it must finally be removed on account of the 

 strong convexity of the dorsal side of the outline. In all true species 

 of Indiana the back is straight. In size, too, they greatly excel I.f 

 minima, the length of the latter being only about 1.1 mm. 



Occurrence. — Drifted glauconite sandstone, Aland, Sweden. Prob- 

 ably Middle Cambrian. 



INDIANA? SOLVENSIS (Jones) 



Plate 9, Figure 29 



Leperditia solvensis Jones, Ann. Mag. Nat. Hist., ser. 2, vol. 17, 1856, p. 95, pi. 7, 

 fig. 15. — Salter, Proc. Geol. Soc. London, vol. 20, 1864, p. 238. 



Primitia solvensis Jones and Holl, Ann. Mag. Nat. Hist., ser. 4, vol. 2, 1868, 

 p. 55 (footnote). 



Assuming that the original type of this species is really of Cambrian 

 age, and being convinced that true Leperditiidae were not developed 

 before the close of the Ozarkian period, it is deemed advisable to refer 

 it to the Cambrian genus most suggested by the meager description 

 and figure pubHshed by Jones. According to the latter, a copy of 

 which is given on Plate 9, it seems to agree best with species of 

 Indiana, the outline suggesting /. lippa rather more than any of the 

 others. Jones describes the ends and ventral margin as having "a 

 well defined, flattened, marginal rim," a feature that, while unusual 



