MUREX ROCK SHELL. 95 



according to the arrangement of these ornaments. 

 One division of shells called Ramella,* Frog, 

 from their resemblance to that animal, are dis- 

 tinguished by having two varices in each whorl, 

 and these are continued in a longitudinal series 

 on each side up to the apex, giving the shell a 

 flattened appearance on the front and back. 



The shells of another division")" are distin- 

 guished by three rows of varices, so arranged 

 that they form three longitudinal raised lines 

 taking rather an oblique inclination towards the 

 apex. It is evident that the habits of the mol- 

 lusca of these two sets of shells must be diffe- 

 rent, for the situation of the varices of the latter 

 proves that a smaller portion is added to the 

 abode at each epoch of its growth than in the 

 Ramella. 



A third division J of this genus includes shells 

 ornamented by varices, not disposed in a con- 

 tinued series as in the other two classes. This 

 difference in the disposition of these protube- 

 rances is occasioned by the piece which the ani- 

 mal adds to its shell being more than half a volu- 

 tion. The varices are consequently few, and 

 appear scattered over the shell. 



MUREX Ramosus. 

 BRANCHED MUREX. 



Specific character. Shell oval, somewhat 

 nodulous, with three foliated varices ; beak short 



* Plate IV. fisrnre 2. f plate IV - fi nre 1. 



t Plate IV. figure 3. $ Plate IV. figure 1. 



