TRII'OKIS PERVERSA. 425 



Miocene : Vienna basin, Touraine, Belgium, northern Italy. 



Pliocene — Upper and Lower : Italy. 



Pleistocene : Livorno. 



Remarks. — This species, generally a rare form, is recorded as recent from 

 southern seas only, and abroad as fossil from the Miocene to the Pleistocene. As 

 a Crag shell it occurs in the Coralline Crag and very occasionally in the Waltonian. 

 It seems to have been one of the Miocene species which were dying out in the 

 Anglo-Belgian basin at the commencement of the Red Crag period. I have no 

 note of it from any English horizon later than that of Oakley. 



The list of references here given will show that our best authorities are by no 

 means agreed as to the more correct generic and sub-generic names of this little 

 shell. Those I have adopted must be regarded, therefore, as provisional. 



Genus TRIFORIS, Deshayes, 1824. 

 Triforis perversa (Linne), var. adversa (Montagu). Plate XLI, fig. 25. 



1758. Trochus 2)erversus, Linne, Syst. Nat., ed. x, p. 760, no. 523. 

 1803. Murex adversus, Montagu, Test. Brit., vol. i, p. 271. 



1848-74. Cerithium adversum, S. V. Wood, Mon. Crag Moll., pt. i, p. 72, pi. viii, fig. 8, 1848 ; C. per- 

 versum, var. Belli, 1st Suppl., pt. ii, p. 181, add. pi., fig. 17, 1874. 

 1853. Cerithium adversum, Forbes and Hanley, Brit. Moll., vol. iii., p. 195, pi. xci, figs. 5, 6. 

 1856. Cerithium perversum , Homes, Foss. Moll. Tert. Wien, vol. i, p. 414, pi. xlii, fig. 20. 

 1867-71. Cerithium perversum, Jeffreys, Brit. Couch., vol. iv, p. 261, 1867 ; vol. v, p. 217, pi. lxxx, 



fig. 5, 1869; Triforis perversa, in Prestwich, Quart. Journ. Geol. Soc, vol. xxvii, pp. 142, 487, 1871. 

 1870-98. Triforis adversa, A. Bell, Ann. Mag. Nat. Hist, [4], vol. vi, p. 215, 1870; Journ. de Conch., 



vol. xviii, p. 350, 1870; Trans. Eoy. Geol. Soc. Cornwall, vol. xii, p. 144, 1898. 

 1872. Triforis perversa, A. and R. Bell, Proc. Geol. Assoc, vol. ii, pp. 204, 210. 

 1873-5. Triforis perversa, Seguenza, Boll. R. Com. Geol. Ital., vol. iv, p. 356, no. 224, 1873 ; vol. v, 



p. 280, no. 88, 1874; vol. vi, p. 344, no. 424, 1875. 

 1874-92. Cerithium perversum, Van den Broeck, Aim. Soc. Roy. Malac. Belg., vol. ix, p. 292, 1874 ; 



Triforis (Cerithium) perversus, Bull. Soc. Beige Geol., vol. vi (Memoires), pp. 123, 147, 1892. 

 1881. Cerithium perversum, Nyst, Conch. Terr. Tert. Belg., p. 76, pi. vi, fig. 7. 

 1884. Triform perversus and var. adversa, Bucquoy, Dautzeuberg et Dollfus, Moll. mar. Rouss., vol. i, 



p. 209, pi. xxvi, figs. 8-11, 14-17. 

 1890-5. Triforis perversa and vars., Sacco, Boll. Soc. Geol. Ital., vol. ix, p. 190, no. 2128 ; p. 326, 



no. 5373, 1890 ; T. (Monophorus) perversus, var. adversa, Moll. Terr. Tert. Piem., pt. xvii, p. 63, pi. iii, 



fig. 62, 1895. 

 1901. Triforis perversa, BiVgger, Norges geol. Unders0g.'lse, no. 31, p. 661, pi. xviii, fig. 13. 

 1908. Triforis (Biforina) perversus, Kobelt, Icon, schalentrag. europ. Meeresconch., vol. iv, p. 131, 



pi. cxxi, figs. 1, 2. 

 1912. Triphora perversa, Cerulli-Irelli, Palaeont, Ital., vol. xviii, p. 151, pi. xxiii, figs. 53-60. 



Specific Characters. — Shell small, sinistral, sub-cylindrical ; whorls about 15, 

 compressed, the last about one-third the total length ; spire elongate, tapering to a 

 fine point; ornamented by longitudinal and spiral ridges which produce closely-set 



