TO GEOLOGY. 157 



GENUS MUREX. Linnaus. 



M. alternata. Plate 5. Fig. 163. 



Description. Shell subfusiform, turrited, longitudinally 

 ribbed, armed with erect spines ; substance of the shell 

 thin; spire elevated, pointed at the apex; suture irregular; 

 spines tubular, alternately placed on and between the 

 ribs ; whorls seven, flat above ; mouth entire, ovate. 

 Length .8, Breadth .3, of an inch. 



Observations. This curious little Murex strongly re- 

 sembles the M. pungens (Brander), plate 3, fig. 82, (M. 

 fistulosus of Sowerby), and that under the same name, fig. 

 81, (M. tubifer of Lamarck and Sowerby). It differs, how- 

 ever, from both. Having them in my cabinet, on com- 

 parison, I find our shell to be more elongate than either, to 

 differ essentially from the fistulosus in having a longer 

 spire and much smaller ribs, and the tubifer in having but 

 one row of spines instead of four. The Murices with the 

 mouth entire, were separated by Montfort, under the 

 name of Typhis, and Cuvier has adopted it as a subgenus. 



It is remarkable that among so many new species of the 

 various genera, only one Murex should as yet have been 

 found in this stratum. In England forty-seven species 

 have been observed, nearly the whole being from the 

 London Clay and Crag. Eighty-nine species are men- 



