PLEUROTOMARIA. 421 



362. Pleurotomaria subdegorata, Munster, 1844, Inferior Oolite variety. Plate 



XXXVI, fig. 10. 



1844. Plettrotomaria subdecorata, Munster. Goldf., Petrel, pi. clxxxv, fig. 3. 

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



p. 445, pi. ccclxiv, figs. 1 — 6. 

 1873. — — — (? non d'Orb.) Tawney, Dundry 



Gasteropoda, p. 44 (36). 



Descriptio 



n 



Height . . . . .30 mm. 



Basal diameter . . . .40 mm. 



Spiral angle ..... 80°. 



Shell turbinate, subturrited, widely umbilicate. Spire regular. Whorls (seven) 

 subconvex and rather flattened posteriorly, sutures subcanaliculate in the later 

 whorls. The ornamentation is regular throughout, consisting of well-cut and 

 slightly undulating spirals, which show beautiful cancellation in the early whorls, 

 and a certain amount of radial striping in the posterior area of the later ones. 



The sinus-band is submedian, prominent, and moderately wide, but does not 

 constitute an angle ; it has spiral ornament similar to that of the whorls, though 

 rather closer. The body-whorl is bluntly angular at the periphery ; base sub- 

 convex and largely umbilicated with strong spiral and radial ornamentation. 

 Aperture subrhomboidal. 



Relations and Distribution. — Near to PL subdecorata, M., this form differs in 

 having the whorls less angular ; yet, on the whole, conforming to Goldfuss' rather 

 than to d'Orbigny's description. It belongs to the Fasciatas, though with a tendency 

 towards the OrnatsB. 



The figured specimen, from Dundry, is the only one of that size from the Inferior 

 Oolite. A much smaller form, about 12 mm. in height, and with six whorls, 

 occurs sparingly in the Concavus-bed at Bradford Abbas and in the " Base bed" at 

 Lincoln. These specimens seem to be truly micromorphs of PL subdecorata, but 

 are rather more turrited and with canaliculate sutures. At present we should 

 not be justified in constituting a new species. 



