Fossil Fa7i)ia, Tabic Cape Beds, Tasmania. 89 



21. Pepisternia semiundulata, sp. nov. Plate II., figs. 10 



and 11. 



►Shell small, ovately fusiform, moderately thick, with convex 

 or subangulated and strongly costated whorls, and a compatively 

 short canal. 



Apical angle about iifty degrees. Embryo consisting of about 

 two-and-a-half convex whorls, the apex of which is slightly excen- 

 tric. The antei'ior fourth of the last embryonic whorl, just before 

 joining the tirst spire-whorl, is closely and slenderly costate, the 

 costee numbering about six or seven, gradually strengthening 

 anteriorly, the remainder of the emljryo being smooth. The spire 

 consists of five very gradually increasing, convex, but occasionally 

 subangulated whorls, with a well-defined and undulating suture. 

 Aperture oval, outer lip thin at the outer edge, but rapidly 

 thickening internally, where it is strongly ridged from the 

 anterior canal to the suture, bearing in this space about twelve 

 or thirteen long ridges, the shallow interspaces being about twice 

 the width of the ridges. Columella bearing one oblique plait at 

 the anterior end of the aperture. Canal somewhat short, very 

 slightly bent to the left and faintly recurved. 



Surface ornamented with transverse costse, strife, and lines of 

 growth closely crossed by spiral threads. The costfe are well 

 elevated and strongest in the anterior half of each whorl, close 

 set, and convexly rounded, the interspaces usually narrower than 

 the costse. lu number the costie increase from nine on the 

 posterior whorl to twelve or thirteen on the body- whorl, and are 

 traversed by parallel lines of growth and fine striae, the latter 

 being usually most noticeable on the posterior slope of each 

 whorl. The transverse ornament is crossed by spiral threads, of 

 which there are about four stronger than the rest developed on 

 the anterior portion of each whorl, and the posterior slope usually 

 bears about three or four finer regularly undulating threads, and 

 in the interspaces there are five much finer threads, of which the 

 middle one is stronger than the pair on either side of it. The 

 intercalated threads are, as a rule, more distinctly visible on the 

 anterior than on the posterior of the whorls. Kody-whorl with 

 about twelve of the stronger threads, and with the finer inter- 

 calations as above. 



Dimensions. — Length, 16 mm.; breadth, 8 mm.; length of aper- 

 ture, 4-5 mm.; breadth of aperture, 3 mm.; length of canal, 4 mm. 



