1919.] E. W. Vredenburg : Shells of the family Doliidce. 155 



umbilicus. Anteriorly to the umbilicus, the terminal portion of the columella is 

 foliaceous and gradually contracts to a point at the anterior end of the shell, its 

 edge being steeply oblique anteriorly towards the left. The columellar lip is not 

 appreciable posteriorly and becomes distinct only anteriorly where it forms the thin 

 flat lamina reflected over the narrow umbilicus. The outer lip is straight and 

 strongly oblique. When fully developed it is bordered externally by a thin though 

 well-defined incised straight line situated at about six millimetres from the actual 

 edge of the aperture. Between this line and the actual edge, the surface expands 

 somewhat outward, the spiral ornaments terminating in slight fimbriations. The 

 external limiting line approximately coincides internally with a slight swelling which, 

 in some specimens, is bifid. Owing to the thinness of the shell, the external spiral 

 ornaments are reproduced on the inner walls in reversed order of relief as is usual in 

 shells of this genus. On crossing the internal swelling of the fully developed outer 

 lip these spiral ornaments remain unaltered in character and do not give rise to 

 apertural tubercles as is frequently the case on the corresponding portion of other 

 species of Dolium. In the great majority of specimens, even those of the largest size, 

 the outer lip terminates in a perfectly simple edge. 



Variability.— -This remarkably abundant shell is particularly constant in all its 

 characters. The only variable features are the more or less sunken disposition of the 

 spire, inconsistencies in the intercalary spiral decoration especially on reaching the 

 adult stage, the variable degree of crowding of the maculations, and slight differences 

 in outline of the body-whorl which may tend to become a little more spherical or 

 spheroidal or else slightly ovoid. These variations are never correlated, but all occur 

 quite independently of one another, so that there is no distinct tendency towards the 

 formation of races or varieties. The most conspicuous abnormality in the orna- 

 mentation is that caused by the adventitious formation of a supernumerary rib as 

 described above in the case of a specimen from Ceylon (or ? Kachh). It is the only 

 available specimen exhibiting this peculiarity which perhaps represents merely an 

 individual aberration. 



Dimensions : — 



Height . . . . . . 114 mm. 69 mm. 



Thickness . . . . . . 93 ,, 55 » 



Height of spire . . . . 25 ,, 10 ,, 



Height of body-whorl . . . . 103 ,, 64 „ 



The larger specimen is from Ceylon (or ? Kachh), the smaller one from Puri. 

 Occurrence. — This is the commonest species of Dolium along the Indian coasts. 

 It abounds wherever the sea-floor consists of fine soft sand or mud. According to 

 Melville and Abercrombie {Mem. and Proc. Manch, lit. and Phil. Soc, 4th ser., 

 Vol. VII, 1893, p. 32) it is a deep-sea form. Nevertheless the shells are frequently 

 washed on to the beach. 



Owing to uncertainties in the identification of this shell and of Dolium tessella- 

 tum, there is some difficulty in ascertaining the limits of its distribution from pub- 

 lished accounts. Judging from the material preserved in the collections of the Indian 



