TROCHOTOMA. 449 



390. Trochotoma Lindonensis, sp. nov. Plate XLI, figs. 8, 8 a, and 9. 



But cf. Teochus quinquecinctus, Zieten. Verstein. Wurt., p. 46, pi. xxxv, 



fig. 2 (Trochotoma quinquecincfa, 

 Zieten, Fischer, Man., p. 848). 



C£. also Teochotoma calix, Phillips. Lycett, Cotteswold Hills, pi. iii, fig. 6 



(fossils of the Fimhria-'dtSige) . 



Description : 



Height . . . . .9 mm. 



Basal diameter . . . .11 mm. 



Spiral angle . . . . . 80°. 



Shell thick, conical, subtabulate, and largely excavated. Spire rather obtuse 

 at the apex, otherwise regular. Number of whorls five to six ; these are angular 

 with a narrow tabular ledge and steeply sloping flanks ; sutures slightly canali- 

 culate. The ornaments are sharp and conspicuous ; the narrow posterior flat 

 area of each whorl is marked by a strong granular spiral line between two deep 

 sulci ; the upper carina at the angle of the whorls is boldly prominent and somewhat 

 subdivided, although there is no actual fissure-band; there is a single spiral rather 

 below the middle of the side of the whorl (fig. 8 a), and this is followed by a sort 

 of double basal keel, which causes the whorls of the spire, except at the extreme 

 apex, to be bicarinate. 



The body-whorl is strongly bicarinate with a very full and bluntly angular 

 periphery, which is spirally striated up to the margin of the excavation. The 

 loop is long and narrow. The aperture is subquadrangular, but curiously indented 

 owing to the sinuous and toothed character of the columellar lip ; the outer lip is 

 thin at the margin, but toothed and grooved internally, in connection apparently 

 with the loop. 



Relations and Distribution. — The Lincoln shells are, in some cases, so well 

 preserved as to exhibit characters which may exist in other British specimens of 

 Trochotoma, but are yet obscured by the plugging of the basal cavity ; hence a 

 comparison with T. calix, for instance, is difficult. T. Lindonensis is related to 

 T. calix jvi&t in the opposite direction to the latter' s affinity for T. gradus. But it 

 is distinguished from T. calix by its more conical outline, higher spire, and narrow 

 tabulation ; also by the invariable bicarination of the spire whorls, and the very 

 considerable difference in the details of ornament. The specimen figured by 

 Lycett as T. calix from the Fimhria-stage of the Cottes wolds possesses some of 

 the features of T. Lindonensis, especially as regards ornament, and seems to be a 

 kind of intermediate form. 



On the other hand, T. Lindonensis presents a strong resemblance to T. quinque- 



