AET. 4 CAMBRIAN CONCHOSTRACA — ULRICH AND BASSLER 67 



to describe them. Only one, the figured type, seems to retain ap- 

 proximately the normal outUne and arrangement of the nodes, and 

 even this was injm'ed along its anterior edge in removing the matrix. 

 Additional material is therefore most desirable. 



Excepting the next following species, no other known Paleozoic 

 fossil is at all Hkely to be confused with good examples of P. mar- 

 ginata. From P. angelini and P. armata, both Swedish species and 

 evidently from older rocks, it is distinguished at once by the mar- 

 ginal rim and folds which seem to be wanting or but ill developed in 

 its foreign congeners. 



POLYPHYMA ANGEUNI (Barrande) 



Plate 8, Figure 30 



Beyrichia angelini Barkandb, Syst. Sil. du Centre Boheme, vol. 1, Suppl., 1872, 

 p. 485. — LiNNARSsoN, Sveriges Geol. Unders., ser. C, No. 21, 1875, p. 45, 

 pi. 5, fig. 11; Of vers. k. Vet.-Akad. Forhandl., vol. 32, 1875, p. 43, pi. 5, 

 fig. 11. 



All that has been learned concerning this apparently well-marked 

 Swedish species is shown in the photographic reproduction on Plate 

 8 of the illustration originally pubUshed by Linnarsson. According 

 to this the valves are semielliptical, the extremities of the hinge 

 equally sharp, and the height less than haK the greatest length, 

 which is about 2.8 mm. A large tubercle is located near the middle 

 of the ventral half, while seven or eight smaller nodes are irregularly 

 distributed over the rest of the surface. The figure does not show 

 a marginal rim, nor is such a feature mentioned in Linnarsson's de- 

 scription. The absence of the rim and of parallel folds within it 

 would suffice in distinguishing the species from its American congener. 

 It may be added further that the outfine differs also in that the hinge 

 is relatively longer and the extremities more sharply angular. 



Occurrence. — Upper Cambrian, Olenus beds, Andrarum, Sweden. 



POLYPHYMA ARMATA (GronwaU) 



Plate 8, Figure 31 



"Beyrichia^' angelini var. armata Gronwall Danmarks Geol. Unders., II Raekke, 

 No. 13, 1902, p. 163, pi. 4, fig. 7, p. 220. 



This form also is known to the authors only from the figure and 

 description published in the Swedish report cited above. Gronwall 

 distinguished it as a variety of P. angelini, but, assuming the pub- 

 lished figures of the two forms to be correct, it is thought a specific 

 separation would have been justified. The principal peculiarity of 

 P. armata lies in the extraordinary development and confluence of 

 the dorsal nodes, which in both of the other species of the genus are 

 much smaller and more numerous. Then there are two conical 

 tubercles that project beyond the ventral edge and add to the dis- 



