PREFACE. 
THIS Work was in the course of printing when the Author 
was prevented from completing it by ill health, in 1820. 
The first 116 pages were actually printed and the plates 
engraved, and more than one copy of the Proofs were in circu- 
lation at the time of its interruption. A Copy of the Proofs 
and the Copper-plates being offered to me for sale, I purchased 
them, and finding on inquiry that the printed Sheets had been 
destroyed, and that the MS. and some impressions of the 
Lithographic plates were in the possession of my friend Mr. 
Thomas Bell, I obtained permission of Dr. Leach’s family to 
reprint the Work, believing that it was an act of justice to lay 
before the public the favourite and the last work of my late 
friend, to whom I am so deeply indebted for the opportunities 
he afforded me of studying zoology. 
Some of the names of the genera and species in the MS., 
when I received it, had been erased and re-written by the 
