26 AMERICAN JOURNAL 



concave and regularly tapering below. Aperture broad above, 

 tapering in advance, canal (from line of growth apparently) 

 straight, moderate in length and narrowed to the extremity. 

 Surface ornamented by long, narrow tubercles, most prominent 

 on the angle of the whorl, each sending a faint rib to the suture 

 above and, on the body whorl, suddenly ending with the greatest 

 convexity of the surface. There are eleven of these on each 

 whorl ; they are crossed, except on the top of the whorl, by nu- 

 merous moderately large revolving ribs, smaller in advance. 



Length about (broken) 3-9 in. ; width, 2*8 in. ; height of spire, 

 2-2 in. : approximate total length, 5'2 in. 



Associated with the following. These two shells are of 

 nearly the same size, but the smaller and more numerous tuber- 

 cles, and the more slender form of the present species will dis- 

 tinguish them at a glance. 



TRITONIUM, Link. 



T. PERNODOSUM, Gabb. 



Shell small, very robust ; spire high, longer than the aperture ; 

 vs^horls six and a half, constricted above and below, close to the 

 suture and bearing large, very prominent tubercles, about seven 

 to a volution. These tubercles are isolated, more or less square, 

 longer than wide, have broad interspaces and are placed on the 

 middle of the upper whorls and on the upper part of the body 

 whorl ; on the body Avhorl they are proportionately smaller and 

 wider apart, and below them the whorl is rapidly narrowed in 

 advance. Besides the tubercles there are about a dozen well 

 marked revolving ribs somewhat alternated in size. In one 

 specimen two large ribs with a smaller one interposed cross the 

 tubercles. Body whorl short and broad ; aperture nearly cir- 

 cular, canal very short ; inner lip lightly encrusted. Varices 

 obsolete. 



Length, 4-5 in. ; width, 2*8 in. ; height of spire above the 

 suture of the body whorl, 2*3 in. ; approximate length of the 

 aperture (broken in advance), 2-2 in. 



From a light greyish brown sandstone near Payta. 



rURPURA, Brug. 

 P. CHOCOLATUM, DucloS. 



Purpura eJiocolatuni, Duclos, Ann. Sc. Nat., Vol. 26, pi. 2, 



%^- . . . 



A single specimen of this species is in the collection. It is 



from a rock made up entirely of comminuted shells cemented by 



