ON MOLLUSCA. 271 
admitted at the present day, and that many authors have de- 
rived excellent hints from his performances. 
Sibbald, in 1684, in his Scotia Illustrata, returned pretty 
nearly to the division of Aristotle, that is, he took into chief 
consideration the abode, from which he deduced the division 
of shells into terrestrial and aquatic, and these last into fluvi- 
atile and marine. 
This was also done by Lister, who, living at a period when 
commerce had brought a great number of shells into this 
country, published a treatise necessarily much more complete, 
under the title of Historie sive Synopsis Methodice Conchy- 
liorum libri Quatuor, &c., in numbers, from 1685 to 1688. 
We find in this work, besides some very excellent figures 
designed and engraved by his daughter, and characters rather 
more rigorously circumscribed, the introduction of the dis- 
tinction of shells according to the equality or inequality of the 
valves. A greater degree of attention is also paid there to 
the hinge of the bivalve shells. 
Tournefort, the celebrated French botanist, who died in 
1708, also endeavoured to facilitate the study of shells, which 
he designated under the general name of testacea, and which 
he defined to be the envelopes of certain animals, which have 
the hardness of a tile or of a vessel made of baked clay ; but 
his method was not known for the first time but by the work 
of Gualtieri, in 1748. This clever botanist substituted the 
names of monotoma, ditoma, and polytoma for those of uni- 
valves, bivalves, and multivalves. Among the monotomes he 
established the distinction of univalves, properly so called, 
spirivalves, and fistulivalves; and in the generic characters 
he paid sufficient attention to the form of the aperture. In 
the class of ditoma he seems to have been the first who estab- 
lished the divisions of bivalves close or open (clause et hi- 
antes). He also gave some attention to the position of the 
hinge. 
