OF CONCHOLOGY. < 



•cated margin straight and very oblique, so as to give the poste- 

 rior basal extremity an angular outline; dorsal margin with a 

 long nearly straight slope in front of the beaks, and nearly 

 straight and horizontal behind them ; posterior dorsal regions 

 flattened and compressed above the carinas Surface with rather 

 strong ridges and striae of growth, crossed on the umbonal re- 

 gions by moderately distinct radiating striae. 



Length, 5*70 inches ; height about 1*51 inches ; convexity, 0-80 

 inch. 



This species, although presenting all the external generic cha- 

 racters of the last, will be at once distinguished specifically, by. 

 its more elongate, depressed form, straigbter basal margin, and 

 especially by the farther anterior position of its beaks. 



The specimen has a little of the anterior extremity and the 

 posterior dorsal margin broken away. The former has been re- 

 stored in outline in the figure by the curves of the marks of 

 growth farther back, and the latter from an impression in the 

 matrix. 



On seeing the typical species of this group in Prof. Swallow's 

 collection, some years back, I at once expressed the opinion that 

 it belonged to an undescribed group that would include his So- 

 len f Missouriensis ; when he gave me the specimen of the for- 

 mer, and loaned me that of the latter. Subsequently he in- 

 formed me, by letter, that he was willing to refer his species 

 Missouriensis to the new group. Consequently I have cited it 

 as above written, as his manuscript name, though it may be 

 proper to state that I do not know whether or not he would agree 

 with me, at present, in placing it provisionally in a subgenus 

 under Sanguinolites. 



Locality and position. Pike County, Missouri, from near the 

 same horizon as the last. 



Note. I have recently seen another fine species of this group 

 among the specimens from the Waverly Sandstone at Scioto- 

 ville, Ohio, collected by the Geological Survey of Ohio, under 

 the direction of Prof. J. S. Newberry, and placed for investiga- 

 tion in my hands. This species may be readily distinguished 

 from both of the foregoing by having its beaks central, and ics 

 posterior umbonal slopes rounded instead of angular, excepting 

 very near the beaks. It measures about 6-50 inches in length, 

 and 2-20 in height. A full description and figures of it will be 

 prepared for publication in the Reports of the Ohio Geological 

 Survey. For this species I would propose the name Sanguino- 

 lites (Promaerus) Andrewsi, in honor of Prof. E. Andrews, of the 

 Ohio Survey, who discovered the typical specimen. 



