TROCHUS. 377 
body-whorl into one thick nodular belt. In this form, also, the umbilicus is, for the 
most part, more completely closed, whilst the ornaments are softer in outline and 
less disposed to be spinous. Specimens are obtained from the lower part of the 
Yeovil Sands at Bridport Harbour in the Dwmortieria-beds, and more rarely in the 
Opalinus-zone of Burton Chiff. 
This tendency to fusion of the duplex carina is also noticeable in certain fine 
specimens of 7. duplicatus from the Parkinsoni-zone of Powerstock, Broad- 
windsor, &c. 
314, TRocHuS suBDUPLICATUS, var. ABBAS. Plate XXXII, fig. 1. 
Description : 
Height : : é : . 24mm. 
Width : : 3 ; 5 PAL conan, 
Spiral angle . 2 F . , Hy —GF, 
Shell regularly conical, scarcely umbilicate; spire elevated, in most cases 
considerably exceeding half of the total height; apex sharp. Whorls seven to 
eight, very concave, and distinctly separated by a considerable suture. There is 
a nodular carina at the posterior and anterior margin of each whorl, the anterior 
one-being usually compound; fine and regular spiral lines ornament the hollow 
portion of the whorls. 
The body-whorl is much excavated and similarly ornamented, the nodular 
anterior carina being excessively thick and complex. The base is rather inclined 
to be flat, and is decorated with fine spiral lines throughout, which are more or 
less puckered by coarse radial lines converging towards the very slight umbilical 
fissure. Aperture subrhomboidal and slightly depressed, with a considerable callus 
on the inner lip. 
Relations and Distribution.—In this very beautiful and highly ornamented shell 
we scarcely recognise our old acquaintance of the Dumortieria-beds. The inter- 
carinal spaces, instead of being smooth, are full of spiral lines, which are also 
conspicuous in the base; the base likewise is flatter and tke aperture more 
depressed. In the general figure there is some approach to 7’. duplicatus, but in 
no other respect. 
Trochus Abbas is characteristic of the Concavus-bed at Bradford Abbas. I have 
one specimen from Burton Bradstock, horizon unknown. It may at once be 
distinguished from the Dumortieria-bed fossils by the fine spiral ornamentation in 
all stages, by its flatter base and larger habit of growth. 
