INSTITUTE OF SCIENCE, PHILADELPHIA. 31I 



slightly overhanging, not discontinuous, whorls; whorls (decollate) nine or 

 more, compact, covered with fine, dense, uniform, often wavy or vermiculate, 

 nearly microscopic sculpture ; whorl broadest at the base, where the margin 

 overhangs the suture and presents a prominent rounded, rib-like edge ; behind 

 this, at not less than a third of the width of the whorl, are from three to eight 

 little-elevated primary spirals irregularly spaced, and slightly undulated by 

 the incremental lines ; suture distinct, not channelled; sculpture fainter on the 

 upper whorls ; base flattish, slightly concave near the edge, spirally striate ; 

 aperture subquadrate with a moderate equatorial sinus. Lon. of specimen 

 figured 64 mm. ; max. diam. of base 28 mm. 



The young have the base extremely concave and the pillar thin, arcuate, 

 and so short that the aperture seems subtriangular. The full-grown shell is 

 the widest species in proportion to its height that I know of, recent or fossil. 

 It seems to be quite rare in the silex-beds. 



Turritella terebriformis n. s. 



Turritella terebriformis Conrad, Cat. Mio. Foss., Proc. Acad. Nat. Sci. Phila. 1S63, p. 

 568 ; name only. 



Older Miocene of the Chipola beds. Burns ; Chesapeake Miocene of 

 Yorktown, Va., Harris. 



Shell acute-conic, with twenty-eight whorls and strong spiral sculpture ; 

 nucleus small, applied at an angle of 30°, followed by about six slender, smooth 

 whorls, after which the spiral sculpture is gradually established ; spiral sculpture 

 on the adult whorls consisting of two basal ridges, rounded or square-topped, 

 the anterior slightly smaller, with an equally wide channel between them ; 

 behind these the equator of the whorl is deeply, roundly excavated ; behind 

 this is another pair of ridges, the posterior the smaller, separated by a shallow 

 sulcus, which as they ascend the spire gradually merge in the early whorls 

 into a single ridge; behind these the whorl slopes evenly to the suture, which 

 is applied below the anterior basal spiral ; the surface also has many more or 

 less evident spiral striae; the transverse sculpture consists of faint undula- 

 tions on the ridges due to accentuated lines of growth ; the adult base is 

 somewhat rounded, with three strong spirals, but which are hardly visible in 

 the young ; pillar short, arcuate, thin, so that the axis of the shell must have 

 been more or less pervious. Lon. of shell 80 mm. ; max. diam. of twenty- 

 eighth whorl 16.5 mm. 



Conrad's type-specimen, which he named but never described, and which 

 Mr. Harris found in the collection of the Academy, enabled us to identify the 

 Chipola fossil with his manuscript name. The specimens from Yorktown 

 differ slightly from the Chipola fossil above described by being less emphat- 

 ically sculptured, the posterior thread of the posterior pair being most gen- 

 erally wanting, but this is a difference such as is commonly found between 

 Northern and Southern specimens of the same species. 



