MUEEX.—FUSUS.— STKOMBUS. 



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 

 {Jig. 64). The animals themselves ^ very closely resemble 

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

 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 Murices properly so 

 called are distinguished by theirshell, 

 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 lamellae. 



12. The Fusus has a canal 

 formed like the common Murex; 

 but the shell is without varices, that 

 is, longitudinal ribs. 



Fig. 64.— MUREX. 



Fig. 65. 



STROMBUS. 



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 (Jio-. 

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

 the adult, into long and slender digitations. 



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? (Strombus, 

 Latin, name of a shellfish.) 



