TROCHUS. 373 



umbilicus, likewise, is of considerable importance, being deep, though not funnel- 

 shaped ; it is encircled by tuberculations of considerable size. 



Relations and Distribution of Trochus Winivoodi. — Mr. Tawney described his 

 species as having the umbilicus closed, but in point of fact this is hardly ever the 

 case with the specimens from Dorset. Small forms are not very far from the 

 conical variety of Trochus sybilla, but the ornaments are always finer, and the shape 

 of the body-whorl different. There are other varieties — almost distinct species. 



Abundant in the Concavus-bed at Bradford Abbas. Occurs also at Stoford and 

 Halfway House, on or about the same horizon. There is a short conical variety at 

 Beaminster, to which a varietal name might be given. 



310. Trochus duplicatus, Sowerby, 1817. Plate XXXI, fig. 10. 



1817. Teochus duplicatus, Sowerby. Min. Conch., pi. clxxxi, figs. 5, 5. 



1852. — — — d'Orbigny, Terr. Jur., vol. ii, p. 275, 



pi. cccxiii, figs. 5 — 8. 

 1867. — — — ?var. Laube, G-ast. B. J. von Balin, p. 10, 



pi. ii, fig. 7. 

 cf . also — — — Tawney, Dundry Gasteropoda, p. 32 (24). 



Non. Tuebo duplicatus, Sow. G-oldfuss, Petref. Germ., pi. clxxix, fig. 2. 

 Non. Trochus duplicatus, Quendstedt. Der. Jura., p. 314, pi. xliii, figs. 18, 19. 



Bibliography, Sfc. — The types of Trochus duplicatus, T. angulatus (cone avus) , and 

 T. dimidiatus came from Little Sodbury ; these are now in the Sowerby type- 

 collection at the British Museum. The village of Little Sodbury is at the foot of 

 the Cotteswold escarpment and on the Lias ; but, as far as I have been able to 

 ascertain, the parish pit in the early part of the century must have been well up the 

 hill and towards the top of the Inferior Oolite. The horizon is doubtless represented 

 in the adjacent quarry on Horton Hill, where the equivalent of the Upper Trigonia- 

 grit of the Cotteswolds {Parhinsoni-zone), yields a number of interesting Gastero- 

 poda. Vide supra, pp. 57, 58. 



Mr. Tawney was, I consider, too comprehensive in his synonymy ; for instance, 

 Quenstedt (loc cit.) expressly says that the species figured by Goldfuss is not that 

 of Sowerby. 

 Description : 



Height . . . . .15 mm. 



Width ..... 155 mm. 



Spiral angle ..... 62°— 66°. 

 Shell regularly conical, moderately umbilicated ; spire elevated, considerably 



48 



