NATURAL HISTORY. 
up in the fishing trawls on the coast. 
NYMPHUM. 1. Gractuz. Leach. Zool. Mise. 
1. p. 45. A frequent species, 
2. N. Femoratum. Zool, Misc. [. p. 45. On 
the shores of the southern coast of Devon. 
CLASS IV. ACARI (of Leach.) 
The animals of this class are chiefly parasitic, 
living on the bodies of other animals, and are for the 
most part subjects for the microscope—they are 
very numerous and open a wide field for investi- 
gation which has been very imperfectly epxlored. 
They have a body composed of a single segment, 
and mostly a rostriform mouth—they breathe by 
means of Trachez, and have six or eight legs ; 
they mostly belong to the Linnean genera Acurus 
and Hydrachna, and were placed by Linneus 
amongst his apterous insects. We can only point 
out a few as specimens of the class, and to complete 
the uniformity of our design, 
ORBITA. Humeratts. (Latr.) Amongst moss 
and under stones ; frequent in the southern parts 
of Devon. 
ACARUS. of Lin. Latreille, and others. The 
Ceummon Cheese Mite. amongst numerous other 
species is included in this genus, 
IXODES. of Latreille and Leach. The Common 
Dog Tick, amongst others is included ia this 
genus. 
HYDRACHNA. Geoarapuica. (Latr.) Inhabits 
