408 GASTEROPODA OF THE INFERIOR OOLITE. 



The following is the original diagnosis : — " Shell conical, regular ; whorls 

 straight-sided, ornamented with rows of separate tubercles, placed obliquely in 

 opposite directions on either side of the sinus-band. Above the band are three 

 rows of compressed tubercles ; below it are three of smaller round tubercles, and 

 then three to four larger ones which form the angle in the last whorl [vide PI. 

 XXXV, fig. 1]. Sinus-band [submedian] with a central salient ridge, and crossed 

 by curved lines ; base of last whorl slightly convex. The umbilicus was probably 

 closed." 



Relations and Distribution. — Tawney was at some pains to point out how the 

 ornaments of this species differ from those of PI. punctata. However, the almost 

 median position of the sinus-band would seem altogether to remove it from the 

 section to which PL punctata belongs. The peculiar Dundry matrix gives 

 emphasis to the ornamentation on which the author largely based his specific 

 characters. 



It is met with sparingly at Dundry, and shells which most nearly approximate 

 to this form occur in the Sauzei-hed, or subzone, at Oborne and Milborne Wick. 

 These have no umbilicus, and the aperture is almost quadrate with a straight 

 inner lip. 



344. Pleurotomaria scrobinula, Deslongchamps, 1848. Plate XXXV, figs. 3 and 



3 a, and ? fig. 2. 



1843. Pleurotomaria scrobinula, Deslongchamps. Vol. cit., p. 60, pi. ix, fig. 4. 

 1854. — — — D'Orbigny, Terr. Jur., vol. ii, 



p. 501, pi. cccxciv, figs 4 — 6. 



Description : 



Height . . • • . 20 mm. 



Basal diameter . . . -20 mm. 



Spiral angle. .... 60°— 62°. 



Shell small, conical, scarcely umbilicated. Spire regular or very slightly 

 convex. Whorls (about seven) flat or scarcely angulated, suture close; the 

 ornaments consist of a tolerably uniform system of fine spirals which are more or 

 less reticulate, the reticulation being best seen in the earlier whorls. 



The sinus-band is almost median, of fair width and prominence, with 

 ornaments which vary from a single spiral with cross-lines (see PI. XXXV, 

 fig. 3 a) to almost smooth. The body-whorl is relatively large and bluntly 

 angular at the periphery ; base rather flat with faint spiral strias, and sometimes 

 a very slight umbilical pit occurs. Aperture rhomboidal to square, the inner lip 

 being straight and reflexed at the extremity so as to form a widish gutter. 



