378 GASTEROPODA OF THE INFERIOR OOLITE. 



315. Trochus spiratus, d'Archiac, 1843, Inferior Oolite variety. Plate XXXI, 



figs. 6 and 7. 



1843. Trochus spibatus, d'Archiac. Mem. Soc. Geol. France, vol. v, pt. 2, 



p. 378, pi. xxix, fig. 4. 



1851. — — — Morris and Lycett, Great Ool. Moll., 



pt. 1, p. 106, pi. xiii, fig. 6. 



1852. — — — d'Orbigny, Terr. Jur., vol. ii, p. 291, 



pi. cccxvii, figs. 16 — 19. 



1853. — — — Morris, Q. J. G. S., vol. ix, p. 326. 



Bibliography, 8fc. — D'Archiac refers to five or six spiral lines as occupying the 

 flat part of the whorls. This species was first noticed in England by Morris and 

 Lycett in the Great Oolite of Minchinhampton, and the same authors recognised it 

 in the Lincolnshire Limestone of Ponton. T. spiratus seems not to be a fossil of 

 the Anglo-Norman basin. 



Description of the Lincolnshire Limestone variety : 



Height . . . . .7 mm. 



Width . . . . .6*5 mm. 



Spiral angle ..... 70°— 76°. 



The relations of width and height vary considerably. The shell is conical and 

 not umbilicated. Spire elevated, but always less than half the total height, acute, 

 but with a slightly flattened apex. Number of whorls five, the apical ones mostly 

 plain, there being seldom any visible ornamentation above the penult, which is 

 angular and possesses two principal and a small intermediate carina. 



The body-whorl is relatively large and angular, and has five prominent spiral 

 lines, of which the two principal, situate at the angle, cause it to be strongly 

 bicarinate. The base is full and spirally striated. Aperture subrhomboidal with 

 a slight tendency to a notch at the columellar extremity. 



Relations and Distribution. — Specimens from Minchinhampton are more conical 

 in outline, and the base is smooth instead of being spirally striated, as is also the 

 case with specimens from Eparcy (Cossmann ' Et. Bath.,' p. 298). In the Lincoln- 

 shire Limestone, specimens from Weldon show strong spiral lines in the base, 

 whilst those from Ponton, on or about the same horizon, are smooth. Hence we 

 might regard the Weldon fossil as a variety. Only found in the Upper Beds of 

 the Lincolnshire Limestone, as far as the Inferior Oolite is concerned. 



