40 MOLLUSCA FROM THE CRAG. 



2. Murex toetuosus. /. 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 sulcata; 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, If 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 

 strias between the ridges, which are seen only in those specimens that are well 

 preserved. Traces of obtuse denticulations within the outer lip may be seen in 

 some specimens. 



Triton,* Montf. 1810. 



Tritonicm. Cuv. Phil. 



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

 tu berculated ; with discontinuous varices placed at irregular distances ; spire more 

 or less elevated, with a rather obtuse apex ; aperture subcircular, or ovate, termi- 

 nating 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 Mediter- 

 ranean. It first appears in the Eocene period, and has greatly increased in number 

 of species in the recent state. 



* Etym. Triton, one of the sea deities. 



