1919.] E. W. Vredenburg : Shells of the family Doliidœ. 159 



are practically straight throughout the greater part of their course, bending backward 

 anteriorly only in the immediate neighbourhood of the terminal zone of accretions 

 which they traverse, as above described, with a pronounced sigmoidal flexure. 



The large semi-circular to semi-oval aperture is anteriorly terminated by the 

 deep, strongly oblique dorsal notch, without any intervening canal. Its posterior 

 termination is slightly though distinctly channelled in the case of immature speci- 

 mens, but becomes simple when the shell is quite adult. The columella which is, on an 

 average, approximately straight, and slightly oblique anteriorly towards the left of 

 the shell, forms an angle of about 120 with the base of the penultimate whorl which 

 it joins rather abruptly. It exhibits two rather feeble winding bulges of which the 

 more posterior one coincides with the inward extension of the zone of accretions, 

 while the more anterior one represents the junction with the reflexed edge of the 

 columellar lip. In the case of small and medium specimens, the anterior part of the 

 columella carries a number of rugosities some of which are sometimes internally con- 

 tinued as thin spiral folds. When the specimens attain a height of about 90 mm., 

 the columellar rugosities become indistinct, while, in the case of fully adult specimens, 

 they entirely disappear, and the columella is quite smooth. The anterior thin foliace- 

 ous terminal portion of the columella, anteriorly to the very small umbilicus, is very 

 narrow. The columellar lip spreads rather widely over the ventral surface of the 

 base. It is mostly so thin as not to interfere with the sculptured and coloured 

 decoration of the base of the penultimate whorl. Nevertheless, in the case of 

 immature specimens its marginal portion, of a glossy porcellaneous texture, is 

 frequently sufficiently thickened to become opaque white, the actual edge adhering 

 fairly closely to the more posterior portion of the convexity of the base, but becom- 

 ing semi-detached or even detached on approaching 'the terminal zone of accretions. 

 Anteriorly to the terminal zone of accretions it surrounds the small umbilicus and 

 joins the columella. The thickened edge gradually becomes less distinct as the 

 specimens grow larger. In the case of full-grown specimens the greater part of the 

 columellar lip ceases to be appreciable, the anterior termination, where it surrounds 

 the umbilicus, alone remaining distinct. In a few specimens, at the posterior 

 termination of the columellar lip, there is a feebly prominent though distinct oblique 

 ridge which contributes to define the shallow posterior channel. The outer lip is 

 straight and strongly oblique. When its structure is characteristically developed, 

 it is externally thickened and expanded, its edge is deeply fimbriated owing to the 

 intervals between the ribs extending much further forward than the ribs themselves, 

 while internally it is thickened and denticulate. All these characters, external expan- 

 sion, marginal fimbriations, internal thickening and denticulations, are as a general 

 rule most typically developed in small and especially in small-medium specimens, 

 especially those measuring from 55 to 75 mm. in height. In exceptional instances 

 they are still quite typically developed in specimens measuring as much as 80 mm. 

 in height, but as the shell exceeds these dimensions they become more and more in- 

 distinct. When the shell is quite adult, the external thickening and expansion, the 

 marginal fimbriations, the posterior channel, and the internal denticulations entirely 



