Casey — Notes on the Pleurotomidae. 137 



Length of a specimen of 8 body whorls, 32 mm.; width, 8.5 mm. 

 Lower Claiborne Eocene, St. Maurice, La. IndOYiciana Vgn. 



15— Costules of the peripheral raised band carried obliquely across the 

 surface between the latter and the subsutural cariniform collar, gen- 

 erally forming a distinct beading on the latter; spiral lines above the 

 posterior end of the aperture very sparse and indi8tinctly defined, 

 below the latter on the body whorl having the form of coarse con- 

 spicuous and widely spaced lyrae, the concave intervals between the 

 lyrae having many close-set striae. Length of a specimen having 6 

 body whorls, 16.5 mm.; width, 4.9 mm. Upper Vicksburg Oligo- 

 cene tenella Con. 



Costules not extending across the rather more deeply concave surface above 

 the somewhat narrower and more strongly elevated peripheral band, 

 the subsutural carina finer and almost even, not at all beaded, the con- 

 cave surface with three or four close-set and distinctly defined spiral 

 lines; body whorl below the periphery with coarse and widely spaced 

 lyrae ; shell similar in form to tenella but a little smaller. Red Bluff 

 Eocene ancilla Csy. 



Costules abruptly confined to the peripheral band as in ancilla, the subsu- 

 tural collar very large, obtusely elevated and coarsely beaded, separated 

 from the peripheral costulose band by a deep abrupt concavity about equal 

 in width to the raised band and bearing a fine and almost even median 

 thread; space below the band with about two close-set and rather fine 

 spirals which are more or less nodulose ; shell differing from the two pre- 

 ceding in its smaller size, shorter and much stouter form and thicker 

 substance, the embryo small and more rapidly pointed. Length of a 

 specimen of 5 body whorls, 9.5 mm. ; width, 3.6 mm. Jacksoniau Eocene 

 of Moody's Branch, Miss nodnlina n. sp. 



Lancea is a rather aberrant species in general features of 

 sculpture but seems to belong to the present genus ; it is rep- 

 resented by a single rather water-worn specimen. The char- 

 acters of alternata are taken from a very careful drawing from 

 the original type kindly lent me by Mr. Aldrich ; Conrad states 

 that lesueurif of Lea, is identical, but the latter is a widely 

 different species, having the anal sinus on the upper concave 

 surface of the whorls. \. number of species, not alluded 

 to above, are known, but not being able to study the types 

 or any accurate drawings, I am unable to include them at 

 present; among these are PL mediavia and equiseta, of 

 Harris, and moniliata of Heilprin. 



It is desirable before discussing the genera of the Surcula 

 type to draw attention to a succession of peculiar Indo-Pacific 

 forms, resembling Pleurotoma in the absence of true ribbing 

 and great development of the spiral carinae, but differing in 



