72 



POPULAR CONCHOLOGY. 



back ; the outer lip somewhat sinuated, and forming, at its 

 junction with the last whorl, an acute angle. — Fossil. 



To this genus belong Natica subnodosa R.oem, Murex 

 tuburosus Sw., and a few others from the Oolite. Mr. 

 Lycett, writing upon the fossils of the Oolite formation 

 in Gloucestershire, says, — " These shells are grouped 

 together in the blocks of stone by hundreds, occupying a 

 vertical thickness of five or six feet, and spread over an 

 area of fifty yards wide, and one hundred long. It is to 

 be regretted that this prolific space will ere long be en- 

 tirely removed ; and the Purpuroidea, in its perfect state, 

 will probably be only matter of tradition as far as this 

 vicinity is concerned."* (Probably by cutting for a rail- 

 road.) 



Monoceras. Lam. — ( Acanthina Fischer : Rudolphia 

 Schum.) — Shell oval ; mouth rather long and 

 notched; a sharp projecting tooth at the base 

 of the right lip; left lip generally flattened. 

 Animal, like the Purpura. — 5 species. 



Found in the seas of southern latitudes, 

 particularly those of America, where they 

 frequent rocks. 



Ricinula. Lam. (Sistrum Montf.) — Shell oval, gene- 

 rally covered externally with spines ; mouth 

 notched and narrow, strongly toothed on each 

 lip, by which the aperture is contracted : 

 spire very short ; operculum horny. Animal, 

 like that of Purpura. — 9 species. 



These shells are usually small, and when ludmda arachnoid cs 

 young have no traces of teeth : they are all 

 natives of foreign countries, and are found principally in 



Monoccras calcar. 



* Annals of Nat. Hist. vol. ii. second series. 



