GASTROPODA. 1051 



Trocboout ubcfMtum I 



TROCHONBMA SUBORABSDM, n. sp. 



I I VTELXXVII. HOB. -M. 



T)i<- t-xt.-f i..r ..f tin- : .rm In In nearly all respects very similar to the Internal east* of T. fragile, and 

 uens were at flret regarded as tMtlferoiu examples of that species. However, un removing the 



11 It-came evident that It Is much thicker, especially at the angles, than It can possibly be In I. 



. .111.1 thai !ii.- Internal cast la much lew angular than are the cants of that species. Indeed, u U 

 ihnwn In tlk'. 33, the sharp external carlna are only obscurely Indicated on the Interior cast. An equally 

 mil-. riant difference, and one that removes the species rather widely from all of the preceding species 

 save T. ixllulum. l the fact that the lines of growth, Instead of continuing their general backward dlrec- 

 tion .>n the peripheral face, are hen- turned forward to form a wide-angled notch as In many species of 

 Lophofjiini. The lines of growth are very flne on the whole with many that are readily discernible to the 

 unassisted eye. On the base they are not as strongly turned backward a* In T. fragile and most other 

 species of the genus, so that the aperture Is not as oblique as usual (compare plate LXX V 1 1, tigs. 15 and 

 30). The upper carlna Is very near the suture and sometimes scarcely removed from It. 



The comparatively slight obliquity of the aperture In this and the next species (T. retrortum) allies 

 t n.'in with the forms Included In the subgenus Eunema. 



Formation and totality. The types of this species are from the upper part of the Trenton group In 

 Mercer and Boyle counties, Kentucky. A single cast of the Interior, apparently belonging here, was found 

 In the Kuslsplra bed near Cannon Falls, Minnesota. 



E. O. Ulrlch (12 specimens). 



Ti:n, HIINKM v I:KI i:<.i:-i M. n. >//. 



PLATE LXXVII, ri08. ! 



In most respects like T. tubcrtutum, but the mouth Is even less oblique, the umbilicus narrower and 

 much more abrupt, the shell thinner, the Inner Up stralghter, and the lines of growth even finer and more 

 regular. The almost vertical wall of the umbilicus and the very slight backward curve of the lines of 

 growth on the base of the shell are two very striking features when the species Is compared with T. 

 vmMteahtm and other species of thtt type. The mouth Is pentagonal, the upper carlna very near the 

 suture. 



and locality. Ctenodonda bed, Black River group, Goodhue county, Minnesota. 

 CWtartm.-E. O. Ulrlch. 



TROCHONEMA MADISONENSB, n. sp. (Ulrich.) 



I'l.ATE LXXVIL F108. -. 



A large hell agreeing In most particulars with T. umbilicatum, but having relatively higher and 

 more ventricose whorls, while the ridge, which generally surrounds the umbilical depression in this genus, 

 Is quite obsolete. The shell Is thicker, the surface markings stronger, the mouth very oblique and with 

 thicker lips. Casts of the Interior of the two species are more alike than their exteriors, yet those of the 

 present may be distinguished by the greater separation of the whorls du<- to the removal of a greater 

 thickness of shell. There In a wide u-.t.-i. In the outer and upper portions of the perltreme which, with 

 the somewhat triangular form of ih<> aperture In a ventral view, suggests relations with T. eectntncum. 

 Figures of that shell are given on the same plate with those of this species, so it Is scarcely necessary t<> 

 compare them furtln-r 



Formation and locality- Ilichmond group, Madison, Indiana. 

 CWleeton.-E. O. Ulrlch. 



