320 MURICIDiE. 



front, with small angular corners, rounded or bluntly pointed 

 behind. 



Shell conic- oval, rather solid, nearly opaque, somewhat 

 glossy : sculpture, numerous laminar longitudinal ribs (about 

 20 on the body- whorl, and 25 on the penultimate), which are 

 folded or incline towards the mouth; they extend to the 

 suture, but not to the base or the canal ; the surface of all 

 the whorls except the upper two is covered with minute and 

 slight, close-set, spiral impressed lines or striae, which do not 

 cause any decussation or make the ribs tubercular ; top whorls 

 smooth and of a polished lustre ; the lines of growth are irre- 

 gular : colour yellowish-white or pale fleshcolour : spire rather 

 short, ending in an abrupt and somewhat truncated point ; 

 apex angular, twisted at first obliquely upwards, and then in- 

 wards : whorls 6-7, convex and rather tumid, the last occupying 

 two-thirds of the shell : suture wide and deep : mouth oval 

 (with a triangular outline, when the outer lip is flattened on 

 the upper part), expanding outwards ; length (exclusive of 

 the canal) a little more than one-third of the shell : canal 

 shorter than in either of the foregoing species of Trophon, 

 slightly recurved to the left, and terminating in an obliquely 

 rounded notch ; externally it exhibits only the marks of 

 growth : outer lip curved, sometimes flattened above and 

 abruptly inflected on the periphery ; edge sharp, somewhat 

 reflected in adult specimens ; inside smooth : inner lip slight 

 and inconspicuous, coating the pillar and upper part of the 

 canal, not continuous with the outer lip : pillar curved, broad, 

 and somewhat flattened : operculum thin, yellowish, irregularly 

 puckered by the oblique lines of growth. L. 0-6. B. 0-275. 



Yar. 1. alba. White. 



Yar. 2. scalaris. Ribs deeper, abruptly truncated and 

 crested at the top of each whorl. 



Habitat : Hard ground in the laminarian and coral- 

 line zones, from 2 to 50 f., on the eastern and northern 

 coasts of England, all Scotland, Shetland, and the 

 southern and eastern parts of Ireland ; Isle of Man 

 (Forbes) ; Goodwick, near Fishguard, 18 f. (J. G. J.) ; 

 Tenby (Lyons); off the Mull of Galloway, 110-140 f. 

 (Beechey). Both the varieties are Zetlandic. It is less 

 common than T. clathratus as a post-glacial fossil, but 



