1919.] E. W. Vredenburg : Shells of the family Doliidœ. 151 



Medium to large, globose, with depressed slightly conoidal spire measuring from 

 one-seventh or even less to two-ninths of the total height. 



The protoconch is relatively large, its visible portion attaining a diameter of 

 four millimetres. This visible portion is depressed and turbinoid and consists of a 

 very small, flattened, coiled nucleus and of three moderately convex whorls separated 

 by somewhat grooved sutures ; this visible portion constituting only the apical 

 portion of the embryonic shell which, combined with the embedded portion, would 

 exhibit, in this, as in all species of Dolium, a globose or ovoid outline ; such embry- 

 onic shells having, on several occasions, been described as belonging to various 

 genera (see Fischer, Journ. Conch., Vol. XI, 1863, p. 147). The protoconch consists 

 of a very highly glazed, transparent, amber-coloured, horny substance. As is usually 

 the case with Dolium, the protoconch is filled with a secondary deposit of porcellane- 

 ous shell-substance supplying an additional support which has ensured the durability 

 of this delicate structure. The protoconch is strongly oblique to the axis of the 

 remainder of the shell. 



The linear junction of the protoconch with the succeeding portion of the shell is 

 straight and strongly oblique, antecurrent to the posterior suture and retrocurrent to 

 the anterior suture. In full-grown specimens the protoconch is followed by three 

 spire-whorls, the height of which does not exceed one-quarter of their width, the 

 maximum width coinciding with the anterior margin. They are separated by chan- 

 nelled sutures. The first half of the first whorl following the protoconch is evenly 

 convex, after which the whorls become angulated at about half their height. Poste- 

 riorly, a primary spiral rib borders the suturai channel, while another rather more 

 prominent spiral rib accompanies the angulation. A third principal rib is usually 

 visible, at least in the later portion of the spire, along the anterior margin of the 

 whorls, though, in some specimens, owing to an extreme flattening of the spire, it is 

 overlapped and concealed by the posterior edge of the next following whorl. There 

 are even specimens in which the sinking of the spire is so exaggerated that the 

 posterior edge of the body-whorl comes to coincide with the second primary rib. 

 Each of the intervals between these main ribs carries several subsidiary spiral threads, 

 three of which are usually particularly conspicuous, representing a median intercalary 

 thread of the second order, flanked by two more threads of the third order ; their 

 respective thickness differing but slightly. There is, in addition, especially at the 

 earlier stages, a more or less complete set of threads of the fourth order, many of 

 which tend to disappear with increasing growth. Nevertheless, in many specimens, 

 several of these threads of the fourth order may be continued throughout the spire 

 and may reach the body- whorl together with the threads of the second and third 

 orders, which invariably persist. Minor inconsistencies are occasionally observed. 

 For instance, in the space anterior to the angulation, which is narrower than the 

 space between the angulation and the circumsutural rib, one of the threads of the third 

 order may be atrophied, so that this particular interval may carry only two conspicu- 

 ous subsidiary threads instead of three. A singular peculiarity is observed in a 

 specimen from Ceylon (or ? Kachh), in which the anterior thread of the third order in 



