MUREX. 311 



one more on the penultimate), some of which are occasionally 

 varicose, as in M. erinaceus ; all the whorls except the upper- 

 most are encircled by thread-like ridges, of which there are 

 about 20 on the body-whorl, 7 or 8 on the sixth, 5 or 6 on the 

 fifth, 3 on each of the fourth and third, and 2 on the preceding 

 whorl, the whorl and a half which constitute the apex being 

 smooth and glossy ; many of these ridges on the body-whorl al- 

 ternate in size, and some of those below the periphery are often 

 larger and coarser than the rest ; the surface is also covered 

 lengthwise with numerous and close-set twilled striae, which 

 form transverse rows of short vaulted scales on the crests of the 

 ridges upon the lower whorls, the ridges upon the upper whorls 

 being tuberculated : colour dark reddish-brown : spire pro- 

 duced ; apex somewhat cylindrical, with a globular extremity, 

 which is obliquely twisted on one side: whorls 7-8, convex, 

 but compressed upwards ; the last occupies two-thirds of the 

 shell : suture wide, not deep, more or less interrupted by the 

 ribs : mouth exactly oval, expanding outwards ; length (ex- 

 clusive of the canal) five-twelfths of the shell : canal short, 

 turning to the left, covered over on the lower part by the 

 interjunction of the two lips, and terminating in an oval 

 fistulous orifice : outer lip nearly semicircular, sharp and thin, 

 slightly scalloped by the spiral ridges, and sloping inwards 

 to the throat, which is furnished with 6 or 7 small white 

 tooth-like tubercles : inner lip detached at its edges, and re- 

 flected on the pillar and canal; it is continuous with the 

 outer lip at the upper corner of the mouth ; behind it on the 

 lower part is a narrow depression or groove, which separates 

 the new from the old canal, the base being twisted : pillar 

 broad and glossy : operculum reddish-horncolour, rather thin, 

 irregularly laminated, and microscopically fretted ; muscular 

 impressions on the underside elliptical, and nearly central. 

 L. 0-5. B. 0-25. 



Var. ladia. Baycolour. 



HABITAT : Channel Isles, on stony and rocky ground 

 at low-water mark and in the laminarian and coralline 

 zones. I obtained the variety by dredging in 22 f. off 

 St. Martin's Point, Guernsey. Scacchi and Philippi 

 have recorded this species from the Italian tertiaries, 

 and Woodward from the Coralline Crag at Gedgrave. 

 Its existing distribution comprises the North Atlantic 



