THE PALEONTOLOGY OF MINNESOTA. 



tProtowarthlld.T. 



This is the oldest known representative of the suborder, but as all the essential 

 bellerophontid characters are already well developed in it, we should look for, and 

 may confidently expect to find, less advanced forms in the Middle and Lower 

 Cambrian rocks. 



The general expression of 0. antiquata is such that we can scarcely doubt 

 that it is of the type from which the Bucaniidce sprang. The modifications required 

 to reach the latter stage, the formation of an apertural slit with its resulting 

 dorsal band, and a not very great change in surface markings, are quite in accord- 

 ance with the developmental tendency prevailing in early Paleozoic times not only 

 among the Bellerophontacea but among the Eotomacea as well. Further, we are 

 satisfied that Owenella is the stock in which the roots of all the other types of the 

 group, excepting the Cyrtolitidte, are centered. Abundant evidence supporting 

 this view occurs here and there through the following pages. 



PROTOWARTHIA, n. gen. Aperture large but not abruptly expanded, the outer 

 lip bilobate, with a broad and more or less deep sinus but neither a slit nor band ; 

 dorsum convex, never carinate; umbilicus closed; surface markings very fine, gener- 

 ally consisting of more or less obscure crowded lines of growth and delicate 

 revolving striae. The inner lip forms a thin granulose deposit over the dorsum of 

 the inner end of the last whorl and extends on each side around the umbilical 

 region. This portion is covered with interrupted or inosculating lines. Type, 

 Bellerophon cancellatus Hall. 



P. cassinensis Whitfleld sp. Calciferous. P. planodorsata Ulrich. Utica group. 



P. rectangularis U. & S. Stones River group. /'. mihcompressa Ulrich. Richmond group. 



P. pervoluta U. &S. Black Ri v. and Trenton groups. P. concinna U. & S. " " 



P. obesa Ulrich. Trenton group. P. morrmoensis Miller sp. " " 



P. cancellata Hall sp. Trenton and Cincinnati periods. P. bilobatus Sowerby sp. Low. Silur. (Probably 

 P. granistriata Ulrich. Utica group. not American.) 



P. facutilira Hall sp. Hamilton group. 



BUCANELLA, Meek.* (NotKoken.f) Back of shell distinctly trilobate, volutions 

 enlarging rapidly, compressed dorso-ventrally, scarcely embracing; umbilicus large; 

 aperture transverse, the outer lip sinuate; surface markings obscure, delicate, con- 

 sisting apparently of both revolving and growth lines. According to Meek there is 

 no slit-band. Type, B. nana Meek. The European Upper Silurian fossil, Bellerophon 

 trilobatus Murchison, and our common Clinton Bucania trilobata Conrad, probably 

 belong here. 



Unfortunately we have not been able to secure a testiferous example of any 

 of the three species referred to this genus4 Admitting the correctness of Meek's 



Proc Amer. Pbllos. Soc., vol. xl. p. 42; 1870. 



t N. .lahrhiirli I. MiiirralnKlr, etc.. Retlage Band vi, p. 3W); 1889. 



*8liin> thispMne w;is in type we IIMVC. ihrijiijrli (he kindness of I'ruf. K. W. Olaypole ami Mr. Aug. P. Foerste, hoen 

 enabled to sec specimens nf It. li il<ilmtn Conrad sp. which retained some 'if (he shell. This we find to l>e comparatively thick, 

 and marked externally with very fine revolving lines. The lines of growth are very faint and they form a broad sinus on 

 he central lobe of the back about as In I'rotowarthla. There Is no slit-band. 



