38 



Ammonites Carlottensis (N. Sp.) 



Plate VI. 



Fig. 5. 

 Fig. 5. — Outline of aperture of A. Carlottensis, as viewed transversely. 



Shell composed of (apparently rather few) rounded whorls ; umbilicus 

 less than one-half the entire diameter. Volutions encircled b}' faint, 

 though broad, obtusely rounded or subangular ribs, which are alternately 

 bifurcating and simple. Sides bluntly coronated. 



In the only specimen collected, the inner whorls are either covered by 

 the matrix or are wanting altogether. The fossil also has been distorted 

 in such a way as to present nearly an oval shape when viewed laterall}-, 

 so that the proportion of the umbilicus to the entire diameter varies 

 according to the direction in which it is measured. The same distortion 

 seems to have affected the shape of the outer whorl ; at any rate, near 

 the aperture it i'? compressed both at the sides and on the periphery 

 while the other half of the same whorl is inflated, the periphery is evenly 

 rounded, though perhaps a little flattened, and the sides are very much 

 raised. As the inner edge of the whorls is usually rounded, there is no 

 distinct margin to the umbilicus ; in some places, however, the umbilical 

 face of the whorls is steep, but it is never angular above. Measm-ing 

 from suture to suture (of the outer whorl) the inner volutions occupy 

 between one-third and one-half of the diameter of the shell. The aj^erture 

 is always much wider than high ; the emargination at its base (caused 

 by the enci'oachment of the pi-eceding whorl) being moderately deep, or 

 at least, not very shallow. 



The outer whorl is ornamented by nineteen primary ribs ; these com- 

 mence at the sutures, and swell out gradually into obtuse, elongated, but 

 more or less rounded tubercles about the middle or near the inner half of 



