VkBuiMaU ut < 



Hist. Stir. Minn., p. i. 1 : 1 , 1 .!. i "n compari-on it pro\ed to have a thinner shel! 'iiore 



erect ami more rounded in outline. al-o more ventricose ami with a -trouper umbonal 

 ridge, while there are only two cardinal teeth instead of three or more. A fourth 

 form I prop.e scum to de-cribe. in one of tl: Ja, under the name of 



tibbosa. It i- fn.ni the lower Trenton of central Kentucky, and ditler- from 

 the present Bp< . more gibbniis. in having larger unibones, almost 



terminal beaks and more obtu-e anterior - \ tifth is associated with the 



preceding in Kentucky. and also occurs in Tennessee. It is a very thick shell and 

 attain- to larger size than I'. Inujnimn, from which it dill'ers further in its form 

 which is higher and -traiyrhter and more obtuse in front. Hut the principal differ- 

 ence lies in the ligamental area which i- at lea-t twice as high as in adult examples 

 of Satlord's species. The area i- -liown in four specimen- and in all of them its bight 

 urn. or more at the middle and in one it is quite 5 mm. For this form I propose 

 the name Vnim inlin<it'i. Finally a sixth form of this type is known to me 



from aliout tuenty very perfect specimens that I owe to the liberality of Prof. .1. M. 

 Satlord. lit- collected th<-m at " I laynie-." t he locality in Mnith county, Tennessee 

 from which he obtained also tin- types of his "< 'i/rtoilonfa lunjninnn." I 'or the present 

 I .-hall arrange these specimens a- a -mall variety of I'. (//////,/>.;. since they agree 

 much better with that specie* than with true \ . //y/j/V/MO. 



.u/;<m and locality. Tti- 'his species re frmn tin- Tn-nt'm Iniii-tom- inii'lii:.- Nashville 



beds of Safford) In Sniith i-tmntj. T.-nn.- ,. . In K.-iitin-Uy ihi- pecle6 occupies two narrow horizons 

 separati-il In m.,iv th:ui IK> ff-t ( -tr;it;i. Tin- tlr^ Is at the bMe of the Traoton UnMtOOt in M<TC<T 

 nmnty at ;i [xiint alxnit thr. h of Hinh Itrldnr. whi-rc tln> decomposed llmcatone has li-ft 



nunii tfcnnd hori/.n. whii-h i- n.-:ir Hi- t.ji of tin- Tn-iitin, 



;*ed at - i|cm; th. utht-rn niilrMiid N-IWI-PII Itiiivln and DanvilU-. In 



MIIHH--..I . t t t"- iv-trii-N'd to Hi. (iali'iM hul-s. In which It occurs as casts of the 



iur at s'\ - in liiHxihin' county and at St. Paul. 



\ XM'XEMIA SUBl:oTI'NH\ . 



ri.\ 



This species ditler from I . lun/ni'tna SatVorcl .>p.. to which it is doubtless \ 

 closely allied, in its more uniformly rounded outline, broader anterior end and 

 shorter hinge line, and in having the beaks smaller and situated farther behind the 

 anterior extremity. The convexity of the va -o is less, and the >hell is thin- 



ner, particularly in the umboiial and anterior part- where the internal thickening 

 is so little that no perceptible .-ulcus nor rid^e is left in casts of the interior. 

 the same reason the beak- - mu-t be more rounded and larger, so that how- 



ever much the exterior of the two -hells may resemble each other, casts of 

 interior would be distinguished very readih. V. n.ina I'lriiMi. from the upper Trenton 

 in Kentucky, i- a smaller shell: with more ventrico-e val . mbonal 



