224 CEEITHTUM. 



Lamarck, in his "Prodrome,"' selects the following species as 

 typifying the genus : — 



Type. — Murex aluco, Linnaeus. 



Cerithium apheles, Tenison-Woods. 



[Plate VII. Figs. 1,2.] 



1879. Cerithium apheles, Tenison-Woods, Proc. Linn. Soc. N.S.W. vol. iii. 



p. 232, pi. XX. fig. 15. 

 1893. Cerithium apheles, Tate and Dennant, Trans. Eoy. Soc. South Aust. 



vol. xvii. pt. 1, p. 222. 



Shell tapering, about twenty-four narrow, convex whorls ; 

 protoconch composed of four smooth turns, the earliest portion 

 slightly inflated, and the later turns being medially, spirally 

 carinate ; in the brephic stage the whorls are closely spirally 

 sulcate, and these are broken up irregularly by the undulations 

 of growth ; the undulations, being of variable breadth, have, at first, 

 the aspect of varices ; beyond the brephic stage (and this is very 

 remarkable) the irregular longitudinal ribs as a rule become almost 

 obsolete, several whorls being practically smooth, or broadly 

 longitudinally undulating, the spiral sulci being well developed 

 with several smaller striae between. Then, as the animal 

 approached the ephebic stage, there was a recurrence to the 

 longitudinally costate condition which characterized the brephic 

 stage, and these costae become very large and prominent at 

 maturity. Subsequently the ornament undergoes rapid trans- 

 formation. With declining powers, ushering in conditions of the 

 gerontic stage, the conspicuous costae alluded to drop to insignifi- 

 cance and die out, the surface of the whorls bearing only the 

 spiral cords and lineations and the undulating lines of growth. 

 As a final effort, an enormous variciform elevation was then thrown 

 up, much larger and more prominent than any of the longitudinal 

 ornament which preceded it ; after which, permanent senile 

 conditions having been attained, the surface of the body-whorl 

 becomes smooth again, only being interrupted by the lines and 

 slight corrugations of growth and the abnormal development of 

 two or three spiral cords which persist to the end. The aperture 



1 Mem. Soc. Hist. Nat. Paris, 1799, p. 73. 



