INSTITUTE OF SCIENCE, PHILADELPHIA. 383 



operculum varies considerably in different individuals. As a rule, it is not 

 evenly convex and smooth, as usually figured. Such a form I have observed 

 only on a few occasions. Usually the inner side of the operculum is nearly 

 flat, the outer side convex, with a wide, flat subspiral margin sharply impressed, 

 and extending for three-fourths the circumference around the central con- 

 vexity. This latter is also obscurely spiral, with a dimple or depression over 

 the nucleus, where there is also usually a brown stain. At times there seems 

 to be a deposition of callus over all this, and when that occurs the features 

 above described are masked or obscured, but nine out of ten opercula 

 which I have examined show the above-mentioned features, forming a transi- 

 tion to Callopoma quite as. marked as that presented by T. Spenglerianus. 



Section Callopoma Gray. 



Turbo rhectogrammicus n. s. 



Plate iS, figures 8 a, 11. 



Pliocene marls of the Caloosahatchie and Shell Creek, Florida, Dall and 

 Willcox. 



Shell large, compact, rounded, with a rather elevated apex and about 

 seven whorls. Some specimens show a mottled color.-pattern of small white 

 spots on a reddish ground not unlike the pattern observable in some speci- 

 mens of T. crenulatus Gmelin, but the majority of the fossils have lost all their 

 color. The first few turns when perfectly preserved are flat or concave above, 

 strongly keeled at the periphery, with the suture some distance below the 

 keel ; remainder of the whorls spirally sculptured with rounded costse, which 

 increase by intercalation as the shell enlarges, and preserve their relative sub- 

 ordination in size, so that on the last whorl there are spirals of three or four 

 sizes ; the ridge next the suture is particularly strong, and the upper surface 

 of the whorls in front of it is slightly constricted ; the suture is distinct, but 

 not channelled ; across the spiral sculpture the incremental lines are elevated 

 into fine lamella, which are most strongly marked between the ridges, though 

 when perfectly preserved the whole surface bears them ; the spiral in front of 

 the suture, in the early whorls, is occasionally beaded, but as a rule the spiral 

 sculpture, except as cut by incremental lines, is plain and uniform ; the base 

 is rounded, sculptured like the upper surface; pillar broad, excavated, with a 

 prominent fascicle bounding the small, deep subcylindrical umbilicus, but not 

 extended into a point below the aperture ; outer lip thin, body with a moderate 

 callus, grooved near the suture ; throat without lirse, aperture evenly rounded. 

 Alt. 46 ; max. diam. 47 mm. 



Operculum recalling that of C.fluctuosiim Wood in its main features, ex- 

 cept that the narrow lirulae outside of the principal spiral ridge are absent, 

 and the space is, as it were, terraced up to that ridge, while the whole outer 

 surface of the operculum is covered with irregularly disposed, often prickly, 

 pustules. 



