40 MOLLUSCA FROM THE CRAG. 



2. MUREX TORTUOSUS. J. Sow. Tab. IV, fig. 9. 



MUREX TORTUOSUS. J. Sow. Min. Conch, t. 434, fig. 2, 1823. 

 <S. Wood. Catalogue 1842. 

 Nyst. Coq. foss. de Belg. p. 545, pi. 41, fig. 14, 1844. 



M. Testa trigond, fusiformi; transversim late sulcatd ; tribus varicibus angulosis, 

 foliacis, ornatd ; interstitiis nodulosis ; aperturd subquadratd ; canali non clauso, elongato, 

 rectiusculo. 



Shell turreted, fusiform, trigonal, with three sharp varices in each volution, inter- 

 mediate spaces nodulous, and with elevated transverse ridges ; aperture ovate ; canal 

 contracted, but open. 



Axis, 1| inch. 



Locality. Cor. Crag. Sutton. 



Red Crag, Sutton and Walton-on-the-Naze. 



A rare shell in the Red Crag, but more so in the Coralline beds, in which I have 

 met with only a few fragments. It differs from M. erinaceus in having three elevated, 

 sharp, reflected, rather tortuous, and slightly fimbriated varices, in one volution. 

 Upon the spire, or in its young state, these are not so distinct ; they are then numerous, 

 sharp, and elevated : as it grows older, the intermediate ones dwindle into obtuse knobs, 

 which are seen between the varices. It is rugosely striated transversely or along the 

 volutions, with four or five elevated ridges, the upper one of which is the most prominent, 

 giving an angular form to the volution ; it has fine striae between the ridges, which 

 are seen only in those specimens that are well preserved. Traces of obtuse denti- 

 culations within the outer lip may be seen in some specimens. 



TRITON,* Montf. 1810. 

 TRITONIUM. Cuv. Phil. 



Gen. Char. Shell ovate or fusiform, thick and strong, carinated, striated, or tuber- 

 culated ; with discontinuous varices placed at irregular distances ; spire more or less 

 elevated, with a rather obtuse apex ; aperture subcircular, or ovate, terminating in a 

 generally elongated, and slightly curved, or raised canal ; columella lip granulated or 

 plicated ; outer lip thickened and reflected, often dentated within ; and in a living 

 state it has a corneous operculum. 



This genus appears to be intermediate between Murex and Ranella, the former of 

 which has three or more imbricated varices in each volution, while in the latter there 

 are only two, which are regular and obtuse. In this genus they are obtuse and 

 irregular ; sometimes with only a thickened margin to the aperture, formed when the 

 shell has attained its full dimensions. Most of the recent species of this genus are 

 natives of tropical regions, though several are found living in the Mediterranean. It 

 first appears in the Eocene period, and has greatly increased in number of species in 

 the recent state. 



* Etyra. Triton, one of the sea deities. 



