270 CERITHIOPSID.E. 



equidistant ridges on the body-whorl, the uppermost of which 

 is close to the suture and retreats considerably, the lowermost 

 encircles the periphery, and the two middle ones are more 

 prominent ; these ridges are crossed by numerous longitudinal 

 ribs of the same size (from 20 to 25 in the lower of the mid- 

 dle rows), which intersect the ridges so as to form a lattice- 

 work of excavated squares ; the points of intersection are 

 sometimes nodulous ; each of the preceding 5 or 6 whorls has 

 the upper 3 ridges, and is cancellated like the body-whorl; 

 occasionally the penultimate whorl exhibits the 4 spiral ridges ; 

 top whorls smooth ; below the peripheral ridge there is a small 

 and very slight ridge or keel, obliquely winding round the 

 base (which is excavated), and the longitudinal ribs are in that 

 part more or less distinct ; the whole surface is covered by some 

 fine microscopic spiral lines or strife : colour yellowish-brown, 

 the base having frequently a darker or reddish-brown hue ; 

 the body-whorl now and then exhibits two or three obscure 

 bands of the latter colour : spire turreted ; the terminal por- 

 tion is pinched up and very small : whorls 10, rather convex ; 

 the last occupies two-fifths of the shell : suture wide and deep : 

 mouth obliquely rhomboidal, abruptly truncated at the base : 

 its length in proportion to that of the spire is as 2 to 7 : canal 

 extremely short, rather more open than in the last two species, 

 producing a corresponding notch at the base : outer lip semi- 

 circular and somewhat prominent, having the edge scalloped 

 by the four spiral ridges, apparently smooth within ; at the 

 upper corner of the mouth it forms a small sinus or inden- 

 tation as in 0. tubercularis : inner lip narrow and slight, re- 

 flected on the pillar, continuous with the outer lip : pillar 

 very short, slightly curved : operculum filmy, nearly smooth. 

 L. 0475. B. 0-075. 



Monstr. Much narrower, and of an elegant slender shape, 

 quite or almost destitute of longitudinal ribs on the last two 

 whorls, the spiral ridges being consequently very conspicuous. 



Habitat : Coralline zone in Plymouth and Guernsey 

 (J. G. J.); Falmouth (Barlee); Cornwall (Hockin) ; 

 Turbot bank, co. Antrim (Waller). Villafranca (Han- 

 ley). The monstrous form was found by Mr. Hockin 

 at the Land's End ; it has some relation, or at least a 

 resemblance, to the Cerithiurn trilineatum of Philippi. 



