312 GEOLOGICAL SURVEY OF THE TERRITORIES. 



margin straight from end to end, instead of declining forward from the 

 beaks. 



Locality and position: Twelve miles southwest of Salina, Kansas; 

 Dakota Group of the cretaceous series of the Upper Missouri. Pro- 

 fessor Mudge. 



ANISOMYON CENTRALE, (MEEK.) 



Shell depressed, conical, somewhat wider than high, apex central, or 

 very nearly so ; slopes nearly equal all around, or with sometimes the an- ' 

 terior and sometimes the posterior sides a little convex, and the others 

 more nearly straight ; aperture circular ; surface apparently smooth, ex- 

 cepting obscure lines of growth, crossed by several irregular, diverging, 

 obscure, radiating ridges and more strongly defined furrows ; the former 

 being mainly on the posterior and the latter on the interior and lateral 

 slopes. 



Breadth of largest specimen seen, 1.16 inches ; height about 0.95 inch. 



I have seen only two specimens of this species, and these are internal 

 casts, with merely some fragments of the very thin shell remaining, while 

 the extreme apex of both is broken away. The radiating furrows are rather 

 distinctly defined on the anterior slope of the internal cast, while one 

 (apparently not exactly the middle one) is narrower and distinctly deeper 

 than the others on each side of it, which latter are about twice as wide, 

 shallow, and often somewhat divided by a small ridge down the center of 

 each. On the posterior slope one of the ridges is more strongly defined 

 than the others, especially near the apex, and seems to correspond to 

 the deeper farrows of the anterior slope, though not exactly opposite 

 to it. The broken apex in one of the specimens looks as if it might have 

 curved a little backward, though in the other it evidently curved for- 

 ward at the point, if I have rightly determined the relative sides. 



One of the specimens shows obscure traces of the oval muscular scar 

 on each side, and these are connected across the side I regard as the 

 anterior, by a slender line, but the specimen being a little worn on the 

 opposite or posterior side, I have been unable to make out the broader 

 interrupted band that ought to pass around the posterior side, if the 

 species really belongs to this genus. 



This species will be readily distinguished from all of the others yet 

 known from the far western cretaceous rocks by its conical form and 

 elevated apex. 



Locality and position : Box Elder and Colorado City, Colorado j Fox 

 Hills Group of the Upper Missouri cretaceous series. 



TUERITELLA KANSASENSIS, (MEEK.) 



Shell elongate conical, or gradually and regularly tapering from below 

 to the apex, with the lateral slopes of the spire straight ; volutions eight 

 to ten, increasing regularly in size, flattened, or only very slightly convex ; 

 last one rounded below ; suture nearly linear ; aperture ovate. Surface 

 with small, thread-like, revolving lines, varying much in their arrange- 

 ment and distinctness, but usually more strongly defined on the lower 

 half of the last turn ; lines of growth very fine, obscure, and strongly 

 arched or sigmoid, so as to indicate a rather deep sinuosity in the outer 

 lip above the middle. 



Length of large specimen, 1.10 inch ; breadth, 0.34 inch j divergence 

 of slopes of the spire, about 22°. 



This shell varies much in its surface marking, some of the specimens 

 appearing almost smooth, or only showing faint indications of a few 



