TROCHUS. 385 



a rather close suture in the early stage, which becomes wider ; six or seven fine 

 granular spirals ornament the whorls of the spire, the posterior and anterior 

 spiral being slightly the most prominent in some cases, so as to form slight belts 

 in the neighbourhood of the suture. 



In the body-whorl, which is rather tumid, the ornaments become irregular 

 with a tendency to effacement of the spiral lines, but there is often a marked 

 bicarination at the angle of the shell; the angle is rounded off into a full 

 base, which is marked by fine wavy spiral striae. Growth-lines decussate the 

 general ornamentation and are very conspicuous where the spiral lines fail. 

 Aperture subquadrate with some thickening of the inner lip. 



Relations and Distribution. — Trochus substrigosus is a truly polymorphous shell, 

 and when, it develops an additional whorl, we have some difficulty in believing 

 that the species is the same — in other words, that fig. 4 and fig. 11 are different 

 conditions of the same species. 



The more perfect form (fig. 11) occurs sparingly in the ParJcinsoni-zone of 

 Bradford Abbas and Burton Bradstock. Fossils from the Cornbrash of 

 Scarborough exhibit a similar polymorphous tendency. 



324. Teochus Buetonbnsis, Lycett, 1863, Inferior Oolite variety. Plate XXXII, 



fig. 12. 



1863. Tbochus Burtonensis, Lycett. Suppl., p. 99, pi. xlv, fig. 16. 



Description : 



Height . . . . .13 mm. 



Width . . . . .13 mm. 



Spiral angle .... 60°. 



Shell regularly conical, imperforate. Spire elevated, acute ; sutures close. 

 Number of whorls seven, flat and without ornament. Sometimes one of the 

 whorls overhangs a little, otherwise there is hardly any break in the outline of a 

 perfect cone. There is a slight keel at the base of the body-whorl. Base nearly 

 flat and smooth. Aperture subrhomboidal and depressed, with a considerable 

 columellar callus. 



Relations and Distribution. — One would imagine that there should not be much 

 difficulty in finding a name for this perfectly smooth and regularly conical shell. 

 Trochus Halesus, d'Orb., presents some features of resemblance, butM. Cossmann 

 regards that species as an Ataphrus rather than a Trochus. Again Trochus Actsea, 

 d'Orb., has a resemblance, yet we miss the "bourrelet" characteristic of that 

 species. The Inferior Oolite fossil figured in the accompanying plate differs from 



