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Show 142 ON THE SO-CALLED PHYSJE OF AUSTRALIA. [Mar. 19, Physa. The differences, however, between its dentition and that of Bulinus are very considerable, the central tooth being 5-cusped, cusps sharp, instead of 2-cusped, cusps blunt, the extreme marginals being similar in character to the laterals, instead of entirely different, with no trace of serration. Further, the occurrence of the species on an island in the Antilles raises a difficulty on the score of distribution, if its close connection with Bulinus be pressed. It seems, therefore, better on every ground to separate off Plesiophysa, in the expectation that its congeners will hereafter be found rather on the South-American than the African continent. Ameria (H. Ad., 1861) was proposed for Physce with keeled whorls, e. g. P. aliciee, Reeve. The distinction is untenable. Every gradation of keeling is observable in the Australian Bulini, and occasionally the same species is indifferently keeled or perfectly smooth. Glyptophysa (Crosse, 1872\ not 1870; Fischer, 'Manuel') was meant for similar shells, and must share a similar fate. Physopsis (Krauss, 1848) has a truncated columella and lustrous shell. Fischer regards it as a subgenus of Bulinus, but it does not appear that the animal has ever been investigated. There is nothing, therefore, to show that it belongs to Bulinus rather than to Physa. Physastra (Tapp.-Can., 1883) has been dealt with above. Thus reorganized the genus will read as follows:- B U L I N U S , Adans. 1757. Etymology. Diminutive of bulle, a bubble. Synonyms. Isidora (Ehrenb., 1831), Diastropha (Gray, 1840), Ameria (H.Adams, 1861), Glyptophysa (Crosse, 1872), Pyrgophysa (Crosse, 1879), Physastra (Tap.-Can., 1883). Animal without the produced and reflected mantle-lobes of Physa; radula Limnseidan, approaching Planorbis rather than Limneea ; central tooth bicuspid; cusps rather blunt, base square; laterals tricuspid ; marginals serrate. Laterals about 6 to 10, marginals about 25 to 33. Number of rows varying between 140 and 220. Shell sinistral, resembling that of Physa, acuminated or gibbous, smooth or keeled ; texture somewhat thick, covered with a deciduous epidermis; columella strong, often reflected ; umbilicus sometimes very wide and deep. Distribution. Australia, Tasmania, N ew Zealand, N e w Guinea, New Caledonia, Viti and Tonga Islands; Africa, N., N.E., W., and S.; S. France, Spain, and all countries bordering the Mediterranean2. ? Subgenus Physopsis (Krauss, 1848). Animal unknown; shell with truncated columella. Distribution. Natal. 1 Journ. de Conchyl. 3" ser. xii. 1872, p. 151 ; typepetiti, Crosse, and aliciee, Reeve. - Tryon (Struct, and Syst. Conch, iii. p. 101) mentions, but I have failed to trace on what authority, that sinistral Limnaas occur in the Sandwich Islands. His whole arrangement of the present group is destitute of scientific value. |
