176 Dr. Maton's and Mr. Rackett/s 
1. Cochlea. 5. Patella. 
2. Nautilus. 6. Dentalium. 
3. Cypr&a. 7- Concha. 
4. Haliotis. 8. Lepas. 
In some of the subsequent editions of the Systema two or three 
more genera were added ; but, at length, in the 10th they were 
augmented to thirty-two, which are only three less than Linnaeus 
employed on any occasion afterwards. The edition of 17-58 is, 
therefore, to be considered as the period at which he may be said 
to have perfected his principles of Testaceological arrangement, 
though, in fact, the principles themselves underwent no material 
change from the beginning, (a proof that our illustrious author 
never treated the subject with carelessness,) the only alteration 
that he deemed necessary being in the number of the genera : he 
accordingly broke that of Cochlea into Conus, Bulla, Voluta, Buc- 
cinnm, Strombus, Murev, Trochus, Turbo, Helix, and Nerita, and 
that of Concha into Chiton, P/wlas, and the bivalvia. The faults of 
the Testaceological systems which preceded Linnaeus's may be 
readily deduced from the remarks made in various parts of this 
paper. These systems laboured under extreme difficulty of ap- 
plication, not only on account of the multitude of divisions and 
subdivisions which were deemed necessary by their respective 
authors, but also of the practice of founding generic distinctions 
on variations of general contour. Such variations being endless, 
there was consequently no end to the multiplication of families, 
and species became correspondent^ sparing. There was only one 
author who can be said to be free from reproach on this score, 
and that was Adanson : he, however, set out upon principles of 
arrangement essentially different from those of the generality of 
writers on this science, and, by making the contained animal al- 
most exclusively the basis of his system, necessarily became 
limited 
