part 4] THE EYOLUTIO^^ or LIASSIC GASTEOPODS. 815 



close spacing of the spirals, and the low tubercles appear to be 

 elongated in the direction of the spiral. The holotype is slightly 

 worn where exposed, and the true characters of the ornamentation 

 are only seen at the sides. 



The development cannot be made out in this specimen. P. rari- 

 Gostati is probably related to the P. slatteri group, from which it 

 differs in the number of spirals. 



Locality and horizon. — The holotype, the only example of 

 this species that we have seen, is from the Lower Lias {rari- 

 costatus zone) of Churchdown= 



Proceiiithium EQUIRETICULATI7AI, sp. nov. (Tcxt-fig. 6 (( , p. 307.) 



Cf. Cerithium camertonense Moore (12, pi. iv, fig. 9). 



Dimensions of holotype. 



T ,7 -D J. 7 -r ,7 /> • Spiral S^dural 



Lienqth. Hreadtli. Lienqth of spire. -^ ^ 7 



^ .y ./ J" angle. angle. 



12 mm. 41 per cent. 75 per cent. 24° 110° 



Holotype : A specimen in Mr. L. Richardson's collection (L.G. 7), 



A slender shell, whorls convex, with a median carina, ornamented 

 by fine axial ribs, crossing spirals which are somewhat stronger 

 than the axials, producing a network with scarcely perceptible 

 granulations at the intersections. On the last whorl the equi- 

 distant spirals are six in number, the third (counting from the 

 anterior suture) forming a fairly well-marked carina. Mouth 

 simple, or exhibiting a slight sinuosity in the anterior region. 



Development. — -The specimens are well preserved, and conse- 

 quently the early development can be made out. The apex is 

 smooth for about one volution, then a spiral makes its appearance 

 in the anterior region ; on the following whorl axial ornament is 

 established, and extra spirals are added ; by the fourth whorl the 

 spirals number six, and the median carina is already present. It 

 is thus a very accelerated tj^pe. It is important to note that in 

 the early stages the spiral ornament is much stronger tlian the 

 axial, but later becomes less markedly so. 



Locality ?uid horizon. — ^The holotype is from the Lower 

 Lias {armatus -zone) of the railway-cutting, Toddington, near 

 Winchcombe, Grloucester. Similar specimens were found in the 

 Lower Liassic clays at Old Dalby, Leicestershire (now in the 

 collection of the Geological Department, University College, 

 Nottingham). 



Procerithiijm (Exelissa) cf . jstumismale (Tate). (Text-figs. 5 6 

 & 8, pp. 306, 316.) 



Exelissa numismalis Tate (19, p. 417, and 20, pi. xxvi, fig. 5). 

 Cf. JExelissa grata (Terqueui) (Cossmann, 3, pi. v, figs. 2-5). 



Dimensions of our specimens. 



Length. JBreadth. Length of spire. 



6'5 mm. 30 per cent. 80 per cent. 



Spiral 



S/ttio'al 



angle. 



angle. 



23° 



110° 



