2/2 TRANSACTIONS OF THE WAGNER FREE 



from one another by any trenchant differences, but are merely conveniences 

 for dividing an overloaded genus. Some small, slender and delicate forms 

 referred to a subgenus under Alaba by Adams with the name Styliferina, are 

 probably closer to Bittium than to typical Alaba. 



Bittium chipolanum n s. 

 Plate 21, figure 15. 



Older Miocene of the Chipola beds, Burns. 



Shell acute, with four larval, at first smooth, afterward spirally threaded, 

 rounded whorls, and about ten subsequent flattened whorls, widest imme- 

 diately behind the suture ; surface spirally grooved, with the interspaces wider 

 than the grooves, and one especially wide one usually at the periphery; 

 transverse sculpture of about sixteen nearly straight, rounded riblets, usually 

 beginning in front of the suture and growing wider and stronger to the periph- 

 ery, where they cease abruptly, or they may be obsolete or entirely absent; 

 they are usually faint or absent on the last whorl, even when they are strong 

 on the rest of the shell ; base strongly, spirally grooved and threaded, with a 

 single swollen, ill-defined varix about half a turn behind the outer lip; there 

 are no varices on the other whorls except in rare cases ; suture distinct, 

 applied below the periphery so that a single thread intervenes behind the 

 suture and in front of the ends of the ribs ; canal short, straight, wide, shal- 

 low; outer lip thin, not reflected; inner lip slightly callous ; pillar somewhat 

 curved, slender; throat slightly or not at all lirate. Lon. of shell 13.0; max. 

 lat. 3.75 mm. 



Bittium chipolanum var. Burnsii Dall. 

 Plate 21, figure j8. 

 Shell more slender, with several varices. Lon. 13.5 ; max. lat. 3.0 mm. 

 This form has variations in the transverse sculpture similar to the type, 

 but the last whorl is proportionally smaller and the spire more slender and 

 drawn out. Both appear to be extremely abundant in the Chipola beds. 



Bittium permutabile n. s. 

 Plate 2r, figure 17. 



Older Miocene of the Chipola beds, Burns. 



Shell acute, with two very minute, smooth, rounded nuclear whorls and 

 about ten subsequent, also rounded, whorls, with the periphery almost mid- 

 way between the sutures ; suture closely appressed, distinct, not marginate, 

 varices irregular, generally two or three in number, distributed along the 

 spire ; spiral sculpture of numerous fine, close-set, sometimes alternated, 

 rounded threads; transverse sculpture of about nine prominent, rounded rib- 

 lets, bigger at the periphery, narrowing and becoming feeble each way toward 

 the suture ; base spirally threaded, aperture with a feeble canal, short and 



