804 NORTH AMERICAN INDEX FOSSILS. 



633. D. ebenina Dall. (Fig. 1 180.) Miocenic-Recent. 

 Whorls round, a sharp, revolving keel flanked by concave sur- 

 faces at the suture. Ribs narrow, widely separated, gently convex 

 forward ; spirals fine ; aperture elongate ; canal very short. 



Miocenic of San Domingo; Caloosahatchie (Pliocenic) of 

 Florida; Recent in Gulf of Mexico. 



634. D. limatula (Conrad). (Fig. 1179, h.) Miocenic. 

 With concave shoulder and strong, nodulose ribs which begin at 



the angulation and extend below the suture ; no spirals ; var. dis- 

 similis Conrad has the ribs obsolete on the later whorls, sometimes 



Fig. 1180. Drillia ebenina, X Fig. 1181. Mangilia infans. 



2.4. (After Dall.) (After Harris.) 



wholly wanting ; in var. pyramidalis Martin the ribs are strong but 

 the apical angle is much greater than in the typical form. 

 Chesapeakean of Atlantic coast. 



CXCV. Mangilia Risso. 

 Small, differs from Pleurotoma in having the notch at the suture, 

 and in its short truncate canal; inner margin varicose. Eocenic- 

 Recent. 



635. M. infans Meyer. (Fig. 1181.) Eocenic. 

 Aperture and canal about one third of the length; shoulder 



concave, with a spiral just below the suture, and several just below 

 the median (main) carination; of these only one is visible on the 

 earlier whorls, being covered by the later ones. 

 Chickasawan and Claibornian of Gulf coast. 



636. M. parva (Conrad). (Fig. 1179,^.) Miocenic. 

 Concave portion of shoulder very narrow, and near the suture; 



