GASTROPODA. 



nKulrl.l 



hell, retain* no trace of surface markings, represents a distinct species, but the material at hand It 

 ncairely Miiiu-l.'iit i<. ju-tlfv -peclHc Mparatlun. A ul.rdlnuU- designation, however, may be allowable 

 and we therefore suggest thai It be known provisionally as var. depresso. 



h.-r vari.'t> or closely related species occurs In the Fusuplra bed of the Trenton group. We 

 have seen but a single example, a cast of the Interior attached to a piece of stone no that only the upper 

 side l visible. As far as can be seen It agrees with O. tuWaxa in all respect* eicept that the last whorl Is 

 scarcely separated from the Inner turns. Con*lu> ring that the Lower Silurian euomphaloItU are all very 

 restricted In their vertical ranges, ll Is highly Improbable that perfect shells (if tin- later form would 

 agree In all respects with the Stones River group types of the specie*. We vent un- therefore to separate 

 the Funlsplra bed form as var. Mourns. 



Ibrmoffcm and JoeoWy. The typical form occurs In the limestones of the Stones River k-n.up at 

 Minn M-m.esota. Mineral nconsln. and Dlxon. Illinois; var. dtprttta In the lower dlu- 



,tral lime?-' ' th.- same group at Murfreesboro, Tennessee; var. ncyum* In the FusUplra 



IKI! i,f th.- Trenton group at Wykoff, Minnesota. 



ObOseMoML Geological and Natural History Survey of Minnesota (two specimens of typical form); 

 K. O. Ulrlch (<ne specimen '. t pleal form and l-.ih varieties). 



JttWicm Btgitter, No*. 6860, 7302. 



OPHILKTINA ANOULARI8, . */>. 

 PLATE L\\l\ HQ8. O-4S. 



Shell small, 8 mm. wide; 2.3 mm. high; planorblform ; spire flat, under side c/>ncave from the 

 peripheral edge on; whorls In contact, quadrangular or subpentagonal In section; outer side vertical, 

 nearly flat, with a small carlna near Its middle; upper side concave between the elevated band, which Is 

 flat and lies at the outer edge, and a low ridge two-thirds across the whorl, beyond which the surface 

 descend* rapidly Into tte sutural channel. The lines of growth, except that they are somewhat finer, are 

 very much as In O. nbtaxa. Four or flve lines occur In 1 mm. With the aid of a glass of low power the 

 direction of the lines can be made out very clearly on our engravings, special care having been given to 

 this feature. 



We know of no shell found in the Lower Silurian rocks of America that is at all likely to be con- 

 fused with either tin- <>r the preceding species. In the Coal Measures and In the Trlasslc of Europe there 

 are several small forms of Euomphalu* that, aside from the fact that they have no defined band, greatly 

 resemble O. anyulari*. 



Formation and locality. Phylloporlna bed, Black River group, near Cannon Falls, Minnesota. 

 CWUetfon.-B. O. Ulrlch. 



Genus ECCYLIOPTERUS, Remele. 



In pan BayliomjAalia, Suompkalux, Opkileta, Maclurta and Itaphintnmn of authors. 

 RKMKLE, 1888, Zeitschr. d. deutsch. geol. Ges., Band xl. 



! <>r generic characters and general remarks see pages 935 to 938, and page 

 1029. 



To give a better idea of this genus than is furnished by the two Trenton species 

 next described, and particularly to show the e volute character pertaining to some 

 of the species, we have added figures, on plate l.XMV. of two Calciferous forms 

 which have been erroneously referred to Eccyliomphnlus by Whitfield. Otherwise 

 E. otcenanus presents an excellent general idea of the present genus. The "collar" 

 is always a notable feature and especially high in the species mentioned. We have 



