49 



each other, in the same or in different habitats. The shells 

 thus related are, H. Stephens! (Cox) ; H. Du Cani (Cox) ; H. 

 Kingi (Br.) ; H. plexus (Cox) ; H. Irvinse ; H. Savesi ; H. 

 Pasccei (Br.); H. Floodi (Br.); H. spoilata (Cox); H. 

 scrupulus (Cox) ; H. coepta (Cox). 



Mr. Petterd still retains the first three as distinct species ; 

 but I question very much the propriety of retaining more 

 than one, as they are undoubtedly all varieties of one species. 



It is remarkable the close resemblance which the fossil H. 

 Tasmaniensis, from the travertin beds at G-eilston, bears to 

 the group of which H. Stephensi is a member in certain 

 characters, especially in pecuharities of sculpture. The latter 

 group may be considered its living representatives, and it is 

 of the greatest interest to find that this dominant and variable 

 type should have such an extension in time as well as in 

 space, for it is thus another illustration of the accuracy of 

 Darwin's statement that " wide ranging, much diffused, and 

 common species vary most." 



H. Diemenensis (Cox). — The species which rivals H. 

 Stephensi in range, number of individuals, and variability is 

 H. Diemenensis, and it scarcely falls short of the former in 

 the number of species which have been created from its most 

 unstable features. It varies in size, and is found in every 

 stage from pure white to pale brown, and with or without 

 more or less regular bands of colour. It varies, too, in one 

 of its chief characteristics, viz., the more or less sharply 

 excavated umbilicus. Between these described species which 

 are purely varieties, there are trifling differences, and these 

 are bridged over by individuals whose variations insensibly 

 melt into each other as in the varieties ofH. Stephensi. It is 

 found fossil, and gives the principal character to the Helicidse 

 sandstone of Barren and other islands of the Straits. The 

 allied species which Mr. Petterd justly reduces to the rank 

 of mere varieties are H. Thomsoni, M. Daveyensis, H. Atkin- 

 soni, H. Camillse, H. Wellingtonensis. 



H. Sinclairi. — This beautiful shell is also a most variable 

 species in degrees of depression, and especially in its colour 

 and markings ; and uo one who has examined a large 

 suite of specimens can have failed to notice the extreme 

 variability of the latter. It, also, has a wide range, 

 and is found from the margin of high sea level to an 

 altitude of 2000 feet. It is also found fossil associated with 

 four extinct species in the yellow limestone at Geilston Bay, 

 and may therefore be considered the oldest known living 



