GASTEROPODA. 



(\1 



and two claw-shaped lateral teeth ; mantle lax, produced 

 into a siphon, which is not extended much beyond the 

 canal of the shell ; branchial plumes two ; foot oval or 

 sub-quadrate, rather small, posteriorily obtuse.* — 188 

 species f ; also fossil. 



These shells are found in nearly every part of the 

 world; the finest species come from tropical countries, 

 and are remarkably curious. The Murex tenuispina, or 

 Venus's Comb, as it is called, is entirely beset with long 

 sharp spines, which the animal has the power of dissolving 

 and replacing by a smooth and even surface whenever it 

 finds it necessary to remove them, in enlarging its shell. 

 This faculty is also possessed by other species, but it is 

 very conspicuous in the tenuispina. In specimens in which 

 the process is going on, there may be observed a notch 

 formed by this means in the base of the spines, the com- 

 pletion of which eventually causes them to separate from 

 the shell. { 



The animals of M. trunculus yield a purple dye, which 

 was much used by the Tyrians. M. brandaris, another 

 Mediterranean species, was also used for the same purpose. 

 M. erinaceus and cor a Minus are British: the animal inha- 

 bitant of the former is yellowish white, that of the latter a 

 brilliant scarlet colour. § 



Typhis. Montf. — Shell greatly resembling the 

 Murex, but the spines are tubular, particularly 

 the one at the base forming the canal. Animal, 

 externally not to be distinguished from the 

 Murex. — About 12 species; also fossil. 



Soiocrbyi. 



Tritonium. Cuv. (Triton Lam.) — Shell oblong; 



* Forbes's British Moll. 

 t Gray. 



f Reeve's Iconica. 

 § British Moll. 



