TROCHUS. 375 
312. Trocuus Doryanus, d’Orbigny, 1852. Plate XXXI, fig. 12. 
1852. Trocuus Duryanvs, d’Orbigny. Terr. Jur., vol. ii, p. 280, pl. ccexiv, 
figs. 12—15. 
Description : 
Height . : : ‘ =) (mm. 
Width : : : A . 6 mm. 
Spiralangle . ; 3 Oi 
A single specimen from Grove (Parkinsoni-zone), having the above dimensions, 
so nearly accords with the description and figures of d’Orbigny that we seem fairly 
safe in making the identification. 
This little shell has no umbilicus; otherwise it seems to vary from its near 
relative, Trochus duplicatus, in a direction precisely opposite to that of Zrochus 
angulatus. 
The Subduplicatus-group. 
There is a varied series of trochiform shells in the Lower Division of the 
Inferior Oolite, mostly towards the Lias-boundary, which it is convenient to focus 
under * Turbo” subduplicatus, dOrbigny, as the primary division, even if we 
indulge in varietal names. 
313. Trocuus suspupticatus, d’Orbigny, 1850. Plate XXXI, figs. 13 and 14. 
1850. Turso suspupiicatvs, d’Orbigny. Prod., 1, p. 248. 
1852. — _ — Terr. Jur., vol. ii, p. 339, pl. ecexxix, 
figs. 1—6 (notably figs. 4, 5, and 6). 
Bibliography, Sc.—When d’Orbigny, in the “ Terrains Jurassiques,” placed 
Trochus duplicatus, Sow., at the head of the synonymy of “ Turbo” subduplicatus, 
d’Orb., that author appears to have forgotten that he had already (p. 275, 
pl. ecexii, figs. 5—8) accepted Sowerby’s species, which he described and figured 
with his usual fidelity. If anyone doubts the essential difference between 
T. duplicatus, Sow., and T. subduplicatus, d’Orb., let him refer to the figures and 
descriptions in d’Orbigny’s own work. Moreover 7. duplicatus, Sow., and 
T. subduplicatus, d’Orb., besides being very distinct in form, occur on quite 
different horizons. 
