TROCHUS. 371 
307. TrocHus RUPESTRIS, sp. nov. Plate XXXI, fig. 2. 
Amongst the forms more or less related to T. Sandersii is one from the Irony 
Nodule-bed at Burton Bradstock, which almost merits to be named as a distinct 
species, or at least as a variety. 
Description : 
Height and width ; : : . 15 mm. 
Spiral angle . é ‘ eon: 
The apex is more pointed than in 7’. Sanaa and the outline more regularly 
conical. The chief difference lies in the number and position of the spiral belts ; 
the whorls also are less concave, and the base somewhat fuller, and in some 
specimens the umbilicus is smaller. 
Found sparingly at Burton Bradstock, and a variety at Mapperton. 
308. TrocHUs SYBILLA, sp. nov. Plate XXXI, fig. 3. 
Cf. Trocuus Sepewick11, Miinst. Goldf., Petref. Germ., pl. elxxix, fig. 4. 
Description : 
Height : ; ; . 10mm. 
Width : ; : ; 2 l-oamm: 
Mean spiral angle : (ie 
Shell subconical, angulated, shghtly minnie The spire, which is rather 
more than one-third the total height, is very obtuse at the apex. Number of 
whorls five, well separated by the suture. Close to the posterior margin of each 
whorl is a circle of tubercles, between which and the principal keel the whorl is 
concave and sloping ; the principal keel is richly tuberculated. 
This kind of ornamentation is continued in the body-whorl, which is largely 
biangulated, owing to the development of a lower tuberculated keel, close to the 
basal periphery, base moderately full and decussated with spiral and axial lines. 
Tn addition to the fine spiral lines which pervade the whole shell, there is a system 
of radial costee with posterior deflection. A sweep of elongated tubercles encircles 
the restricted umbilicus. Aperture subquadrate. 
Relations and Distribution.—Differs from T. Sedgwickii, Minst., chiefly in the 
less elevated spire and more stumpy character of the shell generally. In fact, this 
is a somewhat abnormal Trochus, serving to remind us of Delphinula angulata. 
Nevertheless 7. sybilla is related to T. Sandersit. 
