TROCHUS. 371 



307. Teochus 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 . . . . . 72°. 



The apex is more pointed than in T. Sandersii, 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. Teochtjs Sedgwickii, Miinst. Goldf., Petref. Germ., pi. clxxix, fig. 4. 



Description : 



Height . . . . .10 mm. 



Width ..... 11-5 mm. 



Mean spiral angle .... 75°. 

 Shell subcorneal, angulated, slightly umbilicated. 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. 

 In addition to the fine spiral lines which pervade the whole shell, there is a system 

 of radial costaa with posterior deflection. A sweep of elongated tubercles encircles 

 the restricted umbilicus. Aperture subquadrate. 



Relations and Distribution. — Differs from T. Sedgwickii, Miinst., 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 T. sybilla is related to T. Sandersii. 



