MUREX. 489 



with all disinterested naturalists, stamp it as a true member 

 of the genus Murex. The animal is lively, active, not at all 

 shy, and marches with rapidity; it inhabits in great abun- 

 dance the littoral and laminarian zones. It must be regarded 

 as the type of the British species of this section ; it has the 

 most intimate and congeneric alliances with the animals of 

 the third and fourth sections. 



M. INCRASSATUS, Muller. 



Buccinum macula, Montagu. 



Nassa incrassata, Auct. et Brit. Moll. iii. p. 391, pi. 108. f. 3, 4 ; 

 (animal) pi. L.L.f.l. 



Animal spiral, of a pale dirty-yellow throughout, marked 

 irregularly on all its organs with small dark lead-coloured or 

 brown dots, lines, or blotches. The branchial fold of the 

 mantle extends far beyond the short canal, and though cloven, 

 forms apparently an entire cylindrical tube, which is con- 

 stantly in motion and used as a tentacular organ. The head 

 is pale red, with a vertical fissure, from which a long probos- 

 cidal trunk issues. The tentacula are not long, but thickened 

 from their bases to half the length, at which point the eyes 

 are fixed at the internal angles; from whence they taper 

 to slender conical points. The foot is truncate anteriorly, 

 indented in the centre in front, and curving right and left into 

 pointed auricles ; when extended it is longer than the shell, 

 and tapers posteriorly to a flat, bevelled, emarginate terminus, 

 with scarcely a trace of caudal filaments ; the operculum is 

 corneous, of suboval shape, and shows the subunguiculated 

 striae of increment. There are two semilunar branchial 

 leaves, one much larger than the other, with dark brown 

 transverse vessels, connected with the mantle and neck in 

 the usual manner; the heart is a pale, minute, subcircular 

 inflation, situate immediately behind the branchiae. The 

 male has on the right side the ordinary spatulate organe 

 generateur, and the testis, which is paler than the ovarium, 

 is substituted for that organ ; in the female the ovarium is 

 large, of a deep maroon-red, mixed up with the pale brown 

 liver, and fills the three terminal volutions. 



