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HORN EXPEDITION—MOLLUSCA. 
Family Physid^. 
Genus Bulinus. 
The differentiation of the Australian and Tasmanian species of Bulinus is 
fraught with the greatest difficulty, as an extensive study of numerous so-called 
species leaves no doubt of their extreme mutability, and that the majority havp 
been established on local races. A very large reduction in the number of names 
(sixty-two) is inevitable, and until the species have been satisfactorily deliminated, 
it may not be possible to employ in every case a nomenclature in accord with the 
rules of priority. It is with some reluctance I admit three species of the genus 
collected by the Expedition, and the names which I employ are not used in a 
collective sense, but rather as a racial expression, whose real affinities have yet to 
be worked out. Thus I have little doubt that B. texturatus, B. puncturatus^ and 
P. tenuisiriatus are variants of one species ; but of these, the figure and description 
of B. texturatus best applies to the shells which I have so named. 
Bulinus texturatus, Sowerby in Reeve’s Icon. 
Storm Creek, River Stevenson, Blood’s Creek, Bagot’s Creek, Palm Creek, 
Lawrie’s Creek, River Darwent and its tributaries. 
Stumpy forms approach B. pectorosus, whilst narrow elate forms approach 
B. dispar. 
Bulinus d is par, Sowerby in Reeve’s Icon. 
Ollara Water, on the River Darwent; Palm Creek. Among those from the 
latter locality, it is not infrequent to find individuals with loosely-coiled spires, 
or even with the last whorl detached. 
Bulinus pectorosus, Conrad. 
Adminga Creek and Reedy Creek. 
IsiDORELLA, gen. nov. 
Since my first acquaintance with the Australian Physidse of the group 
typified by P. newcombi I have considered them entitled to generic distinction on 
conchological grounds. The shell-characters are—form oval, last whorl much 
inflated ; peritreme continuous, adnate to the parietal wall, and forming a false 
umbilicus; no columella, strictly, or columella without a fold. These conform 
