MUREX. FUSUS. STROMBUS. 



55 



dant than in our day ; for, in certain formations, such as the 

 calcareous* tertiary of the environs of Paris, an immense number 

 is found in the fossil state. 



10. In the TRIBE OF MUREX, the aperture of the shell is 

 always prolonged into a canal, either straight or inflected 

 (fits' 64). The animals themselves very closely resemble 

 those of the tribe of Buccinum ; they have a trunk, no veiJ 

 on the head, the right edge of 



the mantle furnished with lobes or 

 filaments, and a horny operculum. 

 They are all carnivorous and inhabit 

 the sea. They are subdivided, ac- 

 cording to the form of the shell, 

 into Murex properly so called, 

 Fusus, Strombus, &c. 



11. The Mu rices properly so 

 called are distinguished by their shell, 

 the canal of which is projecting and 

 straight, and the whorls are furnish- 

 ed with transverse elevations, in 

 form of varices or ridges, which 

 often present spines, or ramified and 

 slashed plates, or lamella?. 



12. The Fusus has a canal 

 formed like the common Murex ; 

 but the shell is without varices, that 

 is, longitudinal ribs. 



Fig. 64. MUREX. 



13. The STROMBUS has a shell in which the 

 canal is straight or curved to the right, and its 

 external edge expands with age, and this canal 

 presents a sinus (hollow) behind, in which 

 the head lodges, when the animal extends 

 itself. In the STROMBUS PROPERLY so 

 CALLED, the sort of wing formed by this prolon- 

 gation of the margin of the shell is entire ( jfor. 

 65), while, in the PTEROCERA, it is divided, in 

 the adult, into long and slender digitations. 



Fig. 65. 



STROMBUS. 



10. How is the tribe of Mu'rex characterised ? (Murex, Latin, a shellfish.) 



11. How are Mu'rices properly so called distinguished ? 



12. What are the characters of Fusus ? (Fusus, Latin, a spindle.) 



13. What are the distinguishing characters of Strom'bus? (Strombui 

 Latin, name of a shellfish.) 



