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DIPSAS. 
CHARACTER GENERICUS. 
Testa fluviatilis, bivalvis, equivalvis, transversa, impres- 
sionibus muscularibus tribus: cardo in utraque valva 
externé lamellitormis. 
ANIMAL ——— 
DIPSAS. 
GENERIC CHARACTER. 
Shell fresh-water, bivalve, equivalve, transverse, with 
three muscular impressions: Ainge in each valve with a 
lamelliform tooth. 
ANIMAL unknown. 
The systematic situation of Dipsas is between the fresh- 
water genera Unio and Anodonta ; genera most widely se- 
parated from each other in the artificial system *, the pre- 
valence of which in Britain, is indeed to be lamented, as 
it not only retards the advancement of science, especially 
in ascertaining the natural affinity of kindred genera, but 
cannot even be rendered subservient to the views of the 
geologist, to whom alone the knowledge of shells, without 
a minute consideration of the animal, can in any manner 
be considered as interesting or useful. 
* The Linnean genus MYA affords an excellent example of the evil 
resulting from artificial arrangement: under this head we find several 
genera with distinct animals and shells, having no affinity with each 
other ; some not even agreeing with the almost unlimited characters laid 
down, many inhabiting the sea, others fresh water, confusedly mixed to- 
gether, without even any distribution into intelligible sections. 
