620 



MISS JANE DONALD ON CARD ONIFEEOUS 



Turritella (pars), J. Sowerby, 1829, ' Min. Conch.' vol. vi. p. 125. 



Buccinum (pars), J. Sowerby, 1829, ' Min. Conch.' vol. vi. p. 128. 



Turritella, W. Hisinger, 1829, ' Esquisse d'un Tableau des Petrifi- 

 cations de la Svede,' i. ii. 



Melanopsis, E. W. Honinghaus, 1830, ' Jahrbuch fiir Geologie und 

 Petrefaktenkunde, von Dr. K. C. von Leonhardt und Dr. H. G. 

 Bronn,' p. 231. 



Cerithium, J. Steininger, 1831, ' Bemerkungen iiber die Yersteiner- 

 ungen welche im TJebergangs-Gebirge der Eifel gefunden werden.' 



Postellaria, J. Phillips, 1836, ' Geol. Yorks.' vol. ii. p. 230. 



Pleurotomaria (pars), J. Phillips, 1836, ib. p. 227. 



Pleurotoma, J. Sowerby, 1839, < Sil. Syst.' p. 612. 



Schizostoma (pars), G. von Miinster, 1840, ' Beitrage zur Petrefak- 

 tenkunde,' vol. iii. p. 87. 



Murchisonia, A. d'Archiac et E. de Yerneuil, 1841, ' Bull, de la 

 Soc. Geol. de Prance,' vol. xii. p. 154. 



Terebra ?, J. Phillips, 1848, 'Geol. Surv. Malvern Hills,' vol. ii. pt. i. 

 p. 357, pi. xiv. fig. 2, non Sow. ' Sil. Syst.' p. 619, pi. viii. fig. 15, 

 nec Phil. ' Pal. Eoss.' p. 99, pi. xxxviii. fig. 182. 



Pleurotomaria (pars), G. & E. Sandberger, 1850-55, ' Versteiner- 

 ungen des Rheinischen Schichtensy stems in Nassau.' 



Pleurotomaria (pars), E. d'Eichwald, 1860, ' Lethsea Eossica,' vol. 

 i. p. 1166. 



The characters of the genus may be thus defined : — Shell elongated, 

 turreted, of numerous, gradually increasing whorls. Aperture 

 longer than wide, with a short or truncated canal at its base ; the 

 columella is arcuated. In some species there is an umbilicus, and 

 in others it is absent. In the outer lip there is a narrow and more 

 or less deep slit, with parallel edges, the successive filling-up of 

 which produces a continuous band throughout the whole length of 

 the spire. This band is sometimes formed by a single elevated keel, 

 or it may be flat and bounded on each side by keels or grooves. 

 The lines of growth on the band are more or less strongly arched. 

 On the upper part of the whorl they curve backwards to the band, 

 and below they curve forwards again, and they indicate the succes- 

 sive positions of the edge of the outer lip. The Murchisonia? are 

 frequently ornamented with keels or tubercles, but they are some- 

 times smooth, with the exception of the band. G. Lindstrom 

 (' Silurian Gasteropoda and Pteropoda of Gotland,' p. 125) states 

 that the " oldest whorls are filled with organic deposit of calcareous 

 matter." On p. 135 he also describes a great peculiarity in the 

 structure of M. clefleoca, viz., the possession of two internal, longi- 

 tudinal keels, continuing throughout the length of the shell, and 

 resembling the interior ridges of the Nerinceas. 



The size of the Murcliisonice varies greatly, some being less than 

 one fifth of an inch in length, while others attain a length of three 

 or four inches. 



The genus Murchisonia is mainly confined to rocks of Palseozoic 

 age. The exact number of species cannot, in the present state of 

 our knowledge, be accurately determined. 



