, ,;.\ 



let} i:i'i;r-TA, n. > 



BryrirMa fkamlrrti II ui .mdWimi I. li, p. UU. pi 4. ! . 



1 lli-r. 



,ii an. I i carapace of tln~ \ariety fmm tin- -.hales of the 



ir Sprint- Mit. 







This designation i- prnp<i-ed for the variety which occurs in the upper beds of 

 the Cincinnati group at numerous localit ies in <hj<>, ln'li;in;i. and Kentucky, :ind in 

 tin- .Mjiuvalent IlinUon Kiver group strata of Minnesota. So far as known it is not 



e found )>flo\v the hori/on of <>,-tliis .tiifn/iiiiilnifn Hall, and Rlitjni-lintrHn <<///</./ 

 'nira-l. It diilei< from the typical form of the species in having all the ridges sorae- 

 \\hat thicker, and the po-t-niedian one much larger. In many cases the latter is 

 nearly or .piite ec|iial to the anterior rid^'f, and extends like it entirely across the 

 \alve. The ventral portion of the carapace also is thicker, and the marginal rid^e 

 >ul>aiij/iilar where the contour turns abruptly inward to the false border. 



anil /<x-o/i/y. Tin' typical form nf ill.- species Is rare In the mlililli- ami ciiininn In the 

 upper thinl of the Trentmi sh:i!es ;it Miir iMul and Cannon Falls. An yet, It ha* not been 



, :iny nf Hie (I ' the (J:ilm:i, nut in the lower l.tils nf the Clnrlnoatl Krnup It Is a com- 



limn fn*il. The var. r<J>n*t<i was fnund in the upper part of the Hinl-"ii KiM-r lial'-- near Sprint' Valley, 

 Minrj i iinlaiitly in tin- up|N-r lii'ils nf thi- Cincinnati k'rnup at Wayi" '! < >xfunl, 



ln<liana, and many other Icx-alltles ID these states. 



Qmia TKTI;.\M:U.\ I'lri.-h. 



Trt: i 1:1. n. I Vio. Jour. C !. xiii. p. 11^. 



/ u/,i, 1'i.Ki. n. INS'.I. Cnntri. ti. Can. Micr...-1'al.. p' l-.ll. " Trl- 



I "nuadr: part.) nf autlmrs. 



Carapace somewhat olilong, often sul|iiadrate, never tumid, with the hinge line 

 straight. Surface deiire~-ed, with a semicircular marginal rid^e; \\ ithin the enclosed 

 space, two, simple or slightly modified, equal or unequal, and more or less nearly 



cal ridges unite helow with the marginal ridge and extend upward from it, one 

 in main tiling to reach the dorsal margin. Free ed/e- u-ually with a -imple 



flattened border; in one case (T. su/,<ju'i<lr(it<i) thick and with the contact mai. 

 concealed by a "fal.-e lender." Surface -niooth or gramr 



Type: P. i/ '/;/. I, in) jiHidriliratti Hall and Whittield. 



