88 Studies in Geology, No. 3 



outer margin. There is a wedge-shaped portion of the 

 upper Hp projecting over the callus. The callus is sharply 

 emarginated below, at about the anterior third, the outer 

 margin making a right-angled indentation, and the callus 

 continuing at about half its upper width ; it extends below 

 into a folding-over of the lower inner peristome. The um- 

 bilicus is situated at the right-angled emargination of the 

 callus. The nuclear whorls are smooth ; the later whorls 

 sculptured by lines of growth. Dimensions : Large mature 

 shell, Height, 55 ; Diameter, 43.5 mm. Medium-sized shell, 

 Height, 31.5; Diameter, 28.5 mm. Young shell, Height, 18; 

 Diameter, 14 mm. Very young shell, Height, 7.5 ; Diameter, 

 6.5 mm. 



This species is very abundant. It is characterized by the 

 sub-plane sides of the whorls, and the peculiar, wedge-shaped 

 callus. It differs very slightly from Polinices stanislas- 

 meimieri Maury,'^^ from the Middle Miocene of Santo Do- 

 mingo ; the spire of subangulata is lower, and the apical 

 angle hence wider; the whorls are flattened on the sides, 

 and not smoothly rounded ; and the callus is wedge-shaped, 

 the margins converging anteriorly, whereas that of stanislas- 

 meiinieri has parallel margins. The chief difference lies in 

 the different apical angle. 



Lower Zorritos ; Variegated. Ridge between Quebradas 

 Heath and Charan, Ouebrada Tusillal, south of Quebrada 

 Pantheon. 



Polynices porcana n. sp. 



Plate IV — Fig. 9. 



Shell fairly large, heavy, the spire low and the apical 

 angle somewhat broad. Whorls about five, well rounded and 

 smooth excepting perceptible growth-wrinkles ; sutures fairly 

 distinct, not channelled. The last whorl of the spire is lower 



"Bull. Amer. Pal., vol. 5, No. 29, p. 136, pi. 23, figs. 15, 16, 

 1917. 



