part 4] 



THE EVOLUTIONS' OF LIASSIC GASTEOPODS. 



331 



interesting to note that, so far as we are aware, they have not been 

 recorded in this countr}'-, although they are highly characteristic of 

 the lowest zones of the Lias in parts of France. 



Locality and horizon. — ^The holotype is a specimen from the 

 Upper Lias of Grrantham (probably /«Zc//^r zone), at Rudd's Brick- 

 works. 



Zygopleuea cf. T.EXIATA (Dcslongcliamps). (Text-fig. 19.) 



Cerithium tceiiiatum Desloiigcliamps (4, p. 200 & ])1. xi, fig. 14). 

 Cf. Zygopleura (Kafosira) tceniata Cossmaini (3, pi. ix, fig. 45). 



Length. 

 7 mm. 



Fig. 19. — Zygopleura cf. 

 tseniata X 6. 



Sutnral 



angle. 



113° 



Dimensions of om- specimens. 



Breadth. Length of spire. anqU. 



29 per cent. 65 per cent. 25'^ 



Fairly slender specimens, Avhorls almost flat, ornamented by very 



tine curved axial ribs ; a well-marked 

 sub-sutural band on the posterior por- 

 tion of each whorl. 



Development. — Apical whorls 

 (about four) not preserved, the re- 

 mainder of the shell is ornamented as 

 described above. 



This specimen differs from Deslong- 

 champs's species in its smaller size, 

 stouter form, and also in the finer 

 ribbing ; from Cossmann's species it 

 differs in having no spirals, and also 

 in the finer and more closely-packed 

 axials. 



Locality and horizon. — The spe- 

 cimen described is from the Lower 

 Lias {^jameRoni zone) of Toddington, 

 Gloucestershire (L. Richardson colL 

 L.G. 1). 



Spiral 



angle. 



23° 



Sutu ra I 



angle. 



105° 



Zygopleuea sEMurECTA (Tate). (Text-fig. 20, p. 332.) 



Chemnitzia semitecta Tate (24, pi. ix, fig. 23). 



Dimensions of holotype. 



Length. JBreadth. Length of spire. 



14 mm. 33 per cent. 67 per cent. 



Holotype : A specimen in the Tate Collection, Museum of Practical Geology, 

 Jermyn Street, London, No. 16416. 



Slender shell with convex whorls and a sub-sutural band ; the 

 ornamentation develops from costate to striate. The mouth is 

 incomplete in the holotype ; but in a topotype, also in the Tate 

 Collection, the mouth is oval, with the appearance of a slight 

 angularity on the anterior margin. 



