1919.] E. W. Vredenburg : Shells of the family Doliidce. 181 



Dolium subfasciatum, Sacco, fossil, more delicately tuberculate than D. muticum, 

 with the labium similarly thickened externally. 



Dolium stephaniophorum (Fontannes), fossil, delicately tuberculated like D. sub- 

 fasciatum, but without the external thickening of the labrum. 



Dolium antiquum, Sacco, also fossil, is only represented by a single incomplete 

 cast, and its specific distinctness from D. muticum is doubtful. 



7th Division. 



This division only contains at present Dölium verrillii, Dall (Bull. Mus. Comp. 

 Zool., Vol. XVIII, 1889, p. 233, pi. xxxv, fig. 12), which is non-umbilicated, and which 

 differs from all other forms of Eudolium owing to the callous thickening of its apertural 

 margins, a character establishing a transition towards the subgenus Malea. The den- 

 ticulations of the outer lip are coarse and apparently simple as is the case to a large 

 extent in Malea. 



Subgenus Malea, Valenciennes, 1833. 



The subgenus or genus Malea includes shells in which the aperture is callous and 

 exhibits coarse denticulations not only along the outer lip, but also along the colu- 

 mellar lip, both opposite the columella and opposite the base of the penultimate whorl. 



8th Division. 



In this division, which may be distinguished as the group of Dolium pomum, the 

 degree of callosity of the aperture is moderate. It includes the following species : — 



Dolium pomum (Linn.), ovoid, with feebly prominent, close-set, broad ribs and 

 without intercalary ornaments. 



Dolium orbiculatum, Brocchi, fossil, distinguished from the foregoing by the 

 somewhat more crowded denticulations of the outer lip. 



Dolium pro-orbiculatum, Sacco (= D. denticulatum, Deshayes sec, Hoernes), more 

 globular than D. orbiculatum, with more even outline of the posterior part of the 

 body-whorl, and with the spire generally taller and more subulate. 



9th Division. 



This division is characterised by the excessive degree of callosity of the aperture. 

 It may be distinguished as the " group of Dolium ring ens." It includes the following 

 species : — 



Dolium ringens (Swainson), large, globose, with numerous fairly prominent ribs. 



Dolium camurum, Guppy (Quart. Journ. Geol. Soc, Vol. XXII, 1866, p. 287, 

 pi. xvii, fig. 9), fossil, differing from Malea ringens in its smaller size, and in the 

 flatter, less sharply defined spiral ribs separated by very narrow, but not deeply 

 sunken intervals; the external decoration therefore somewhat recalling that of the 

 shells belonging to the group of Malea pomum, and establishing a genealogical link 

 between the two groups. In the shortness and prominence of the bunch of folds 

 situated on the base of the penultimate whorl, and in the consequent great depth of 

 the embayment separating it from the anterior columellar group, the shell entirely 

 agrees with Malea ringens, of which it is clearly an ancestral pre-mutation. 



