260 PALEONTOLOGY. 



Formation and locality. — In limestone near the base of the Wahsatch 

 hmestone, of the age of the Waverly group, at Dry Canon, Oquirrh Mount- 

 ains, Ogden and Logan Canons, Wahsatch Range, Utah. Collected by J. 

 E. Clayton and S. F. Emmons. 



ElTOMPHALUS LAXUS. 

 Plate IV, figs. 24-25. 



Euomphalus laxus White, MSS. Lieut. Wheeler's Eept. of Geograph. and Geol. Surv. 

 and Expl. W. of 100th Meridian. 



Shell subdiscoidal; the height of the spire above the body of the last 

 volution equal to from one-third to about one-half its diameter, the inner 

 volutions being scarcely elevated above the general plane. Umbilicus 

 broad and proportionally deep, exposing all the inner whorls. Volutions 

 three or more, seldom, however, exceeding four; rather slender in their 

 proportions; the last one more rapidly increasing in size than the others; 

 obscurely pentangular in transverse section ; the periphery being obtusely 

 angulated just below the middle, slightly flattened above the angle, and dis- 

 tinctly so on the upper surface. The lower side of the volution is gently 

 rounded on the' outer part, but more sharply curved at the edge of the 

 broad open umbilicus. 



Surface of the shell marked by distinct, somewhat irregular, lines of 

 growth, parallel to the margin of the aperture, their direction being nearly 

 at right angles to the axis of the shell, with a very slight sinuosity as they 

 cross the upper flattened surface of the volution. 



The species is a well-marked one, and appears to be quite characteristic 

 of beds near the lower part of the Wahsatch limestone, Wahsatch Range, 

 Utah. It bears a strong resemblance to specimens of E. laxus H. from the 

 Burlington limestones, but the volutions increase much more rapidly, and 

 the flattened space on the upper side is narrower in proportion to the diam- 

 eter of the volution than in those specimens, and it is also a much smaller 

 form. It also bears considerable resemblance to an angulated form in the 

 Burlington sandstones, usually referred to E. cyclostomus H., but probably 

 distinct. There is also a species in the Chemung group of New York very 

 closely resembling this one, but which does not show the angularity of the 



