CRETACEOUS FOSSILS. 177 



angular and stronglj^- shouldered, the upper surface being flattened or a littlo 

 ^'S- ^- concave, with usually a slight outward slope from the sutUi'e 



to the angle or shoulder, where it meets the vertical outer sur- 

 face nearly at right angles ; last or body- volution large, or 

 generally composing about two-thirds the entire bulk and 

 length of the shell; suture well defined by the prominence 

 and angularity of the volutions, but not channeled. Sur- 

 face of each turn ornamented by about ten to fifteen rather 

 strong, vertical, or slightly oblique folds, or costjje, each 

 ,., , of which terminates in a small nodular projection at the 



Pyrguhferahumerosa. ^ '' 



Showing the iiper- shouldcr above, SO as sometimes to impart a subcoronate 

 ture ranch better appearance to the same, while they all become nearly or 



than the specimen 



figured on the plate, quite obsolctc bclow the middle of the body- volution; ver- 

 tical costse crossed by smaller, but quite distinct revolving, raised lines, or 

 small ridges, some four to six of which may be counted on the outer surface 

 of each turn of the spire, and about ten on the body-volution, where they 

 increase in size downward;)''^ upper flattened surface of the volution generally 

 only marked by the moderately distinct lines of growth seen below; aperture 

 obliquely rhombic -subovate, being higher than Avide, rounded-subrectangular 

 above, and narrowed and more or less angular, Avith a slight sinus or notch, 

 at the connection of the outer and inner lips near the middle below; colu- 

 mella arcuate; inner lip, in mature specimens, rather thick all the way up, 

 but more so beloAv, where it is somewhat reflected and margined by a slight, 

 revolving umbilical furroAv, with usually an angular outer margin; outer lip 

 sharp, prominent near the middle, and retreating below and at the angle of 

 the whorls above. 



""^ Length of tlie largest specimen seen among hundreds, 1.63 inches; 

 breadth, 0.90 inch; height of aperture, 0.81 inch; breadth of same, 0.50 

 inch. 



All of the specimens of this shell first studied, as well as all those for 

 some years after brought in, had. the outer lip and loAver part of the colu- 

 mella broken away, so that no very clear idea of the nature of its aperture 

 and the connection of its outer and inner lips below could be formed from 

 them ; Avhile, in all its characters that could then be determined, it so closely 



* These revolving ridges nre represented too coarse in the above figure. 

 12 p R ■ 



