14 SUPPLEMENT TO GREAT OOLITE MOLLUSC A. 



CHEMNITZIA VITTATA, Phil., sp. Tab. XXXI, fig. 10. 



MELANIA VITTATA, Phil. Geol. York., p. 116, pi. 7, fig. 15; 

 CHEMNITZIA VITTATA, D'Orb. Prodr., xi, et No. 29, p. 208. 



Mor. Cat., 2nd edit., p. 242. 

 Oppel. Juraformation, p. 479. 



Testa crassa, turrila, elongata, apice acuto, anfractibus (circa 10) latis, in media sul- 

 depressis, ad suturas elatis, carinis duobus instructis, suturis vaMe depressis ; aperfura, 

 ovafa basi ant/ustata. 



Shell thick, smooth, turreted, elongated, apex acute; volutions (about 10) wide, rather 

 depressed in their middle parts, elevated both above and beneath near to the sutures, 

 forming two narrow, equal, cord-like carinse ; the sutures are deeply impressed ; the aper- 

 ture is ovate, rather small and contracted towards the base, where the extremity of the 

 columella is conspicuous ; the last volution is rendered somewhat angulated by the promi- 

 nence of both the encircling carinaa ; the surface is shining, with large plications of growth ; 

 a magnifier also discloses delicate, nearly regular, distantly arranged, encircling, granu 

 lated lines (about 20 to a volution), or when the surface has been slightly abraded, they 

 appear as punctated striations. 



Length, 4| inches; transverse diameter of the last volution, 1 inch ; the height of each 

 volution is equal to 3-5ths of its transverse diameter. 



The general figure is that of a lengthened cone, and the outline does not exhibit that 

 step-like figure seen in some other allied species, as in Chemnitzia turris (Desl.), C. coarc- 

 taia (Desl.), and C. condensata (Desl.). The two narrow and equally elevated cord-like 

 cinctures which bound each volution, together with the somewhat angular figure of the last 

 volution, separates it from the foregoing and all other known examples of the genus ; 

 perhaps the encircling granulated lines may also constitute a good distinctive character 

 but it can only be discovered in very well preserved specimens. A Chemnitzia, in the 

 Inferior Oolite of the Cotteswolds and of the south-western counties, which does not 

 appear to have been figured or described, approaches near to C. vittata, and has sometimes 

 been regarded as identical with it ; there can, however, be no difficulty in separating 

 specimens of the two forms, when they are well preserved. The Inferior Oolite shell is 

 somewhat less conical, or more subulate ; the sides of the volutions are more flattened ; the 

 upper cincture is rounded and distinct, but comparatively small ; the lower cincture is 

 angulated, and not cord-like; the last volution is destitute of the prominent lower cincture, 

 which imparts an angularity to that part in the Cornbrash shell ; the general figure of that 

 volution is more lengthened and pyriform, so that the base of the aperture is wider and 

 more produced. The Inferior Oolite shell also does not exhibit any trace of the encircling 

 granulated lines ; but possibly the test has not been preserved with sufficient delicacy to 



