184 GASTEROPODA OF THE INFERIOR OOLITE. 



Shell subelongate, rugose; spiral angle nearly regular. Whorls about ten, 

 short, and separated by a wide sutural sulcus. The ornaments consist of two 

 very strong spiral bands, which are grossly nodular (papillas) at the intersection 

 with the longitudinal costaa. These latter are seven or eight in number, and but 

 slightly interrupted ; the amount of inclination or twist is very slight. 



Body-whorl small ; base depressed and marked with strong spiral lines. 

 Aperture suborbicular, with a short and thickly encrusted columella; indications 

 of the groove or furrow at the posterior angle. 



Relations and Distribution. — Distinguished by its very coarse tuberculation, 

 and by having only two spiral bands. A single specimen from the Parkinsoni- 

 zone of Grove. 



114. Ceyptadlax, cf. undulata, Quenst., 1858. Plate XI, fig. 14. 



1858. Cekithium undulatum, Quenst. Der Jura, p. 488, t. 65, fig. 24. 



1860. Tueeitella undulata, Quenst. Heb. and DesL, Foss. Mont.-Bellay, p. 49, 



pi. vii, figs. 13, a — c. 

 Cf. also Cekithium htsteix, Besl. Mem. Soc. Linn. Norm., vol. vii, p. 195, pi. s, 



fig. 47. 



Bibliography, Sfc. — T. undulata was very doubtfully described as a Turritella by 

 Hebert and Deslongchamps, who remark that it has some resemblance to 

 Cerithium hystrix, Desl. In the latter, they say, the whorls are more concave, 

 the spiny tubercles of the anterior and posterior spiral belts (cordons) are more 

 numerous, whilst the costas do not form a regular longitudinal series, but suffer 

 interruption. 



Description. — Probable length 40 mm. ; spiral angle about 12°. Whorls 

 numerous, polygonal, widely separated by the sulcus of the suture. Each whorl 

 possesses a pair of prominent spiral bands or keels near the sutures ; numerous 

 fine spiral lines occupy the intermediate area. The costas are stout, wide apart, 

 and extend nearly from suture to suture, but are irregular in sequence. They ar3 

 about six in number. At the points where the costee decussate with the two 

 spiral bands are very spiny tubercles, which give a rough aspect to the shell. 

 Other indications wanting in English specimens. 



Relations and Distribution. — The species to which I now draw attention is 

 very rarely found in the Parkin soni-zone of South Dorset, and hitherto only in 

 fragments. It is probably intermediate between G. hystrix and G. undulata. The 

 former occurs somewhat rarely in the Bajocian of Normandy. 



