136 ANNALS NEW YORK ACADEMY OF SCIENCES 



Gastropoda 



Orestes subgen. nov. 



This name is introduced for a group of pleurotoinarioid shells which have 

 a shape generally conical or slightly turreted with a gently convex basal por- 

 tion. The band is not very strikingly defined and has a peripheral position 

 distinctly below the middle of the whorl. The upper surface is in general 

 flattened and oblique, with the zone which lies just below the suture more or 

 less prominent and marked by nodes. The sculpture consists of fine, decus- 

 sating, revolving and transverse lira?. The slit band is relatively broad and 

 carries one or more revolving lirse which are sometimes nodulose and occa- 

 sionally conceal to a greater or less degree the structural character of this 

 part of the shell. The slit has not been observed in any of the specimens 

 seen, but it was probably short. The umbilicus was apparently closed, but a 

 reflexed portion of the lower part of the outer lip produces a small excavation 

 which resembles a minute umbilical opening. 



The inner lip is without a callosity. In fact, the mantle seems to have had 

 the power to resorb the shell on the inner side of the aperture, so that this 

 portion of the preceding volution is smooth and slightly depressed below the 

 external ornamented areas. This has been observed in many specimens and 

 is surely not an accidental character. 



In one extreme, these shells suggest Euconospira, from which they 

 differ in their less regular, conical shape, and in the development of 

 nodes below the suture and of revolving lirae in the slit hand. The}' sug- 

 gest also Phanerotrema, but have a more conical shape with a slit band 

 at once broader, less defined, marked by distinctive sculpture and situated 

 not near the middle of the peritreme, but well below. Worthe7iia is in 

 some respects the most nearly related group, at least in the ornamented 

 character of the slit band. Worthenia has the band above the middle 

 rather than below, narrow instead of broad, and with the lunules in the 

 band much more prominent than the revolving lirse (in Orestes the 

 lunules are hardly more than lamellose growth lines), and it has a more 

 turreted, less conical shape to the whole. It is doubtful if any of the 

 groups mentioned have the peculiar eroded or resorbed character of the 

 inner side of the aperture. 



Orestes, then, is referred to a subgeneric position under Worthenia, 

 although its relationship to Phanerotrema is also obvious. The generic 

 name is introduced in honor of Orestes St. John, one of the early paleon- 

 tologists of the United States and one of the early geological explorers of 

 Oklahoma. 



Type species, Orestes nodosus. 



