principally marine, found on the South Coast of Devonshire. 15 
county produces, and, as far as I have the means of ascertaining, 
has not been described ; at least nothing sufficiently correspond- 
ing in character appears in Gmelin. 
ONISCUS. 
ONISCUS CERULEATUS*. 
Tas. IV. Fig. 2. 
Body subcylindric, of a resplendent blue, and destitute of 
joints : the head is conic and pointed : the thorax, which appears 
to consist of two ventricose joints, is of a pale colour like that. 
of the head : antenn four, setaceous, the interior pair longest, 
with three visible joints each: eyes two, large, black and reti- 
culated : legs ten, two pairs of which are affixed to the thorax, 
and the others to the abdomen: the tail is flat, with five strongly 
defined articulations, and furnished with five caudal fins, the 
middle one largest and conic, the lateral ones ovate, and furnished 
with long bristles ; this part is nearly the colour of the head and 
thorax, pale brown.. The under part of the body is equally con- 
vex and of the same colour as above, appearing under the mi- 
croscope to. be destitute of any division: this crustaceous 
covering is subpellucid, and in some lights is a little shaded by 
the intestines. 
It swims with the head foremost, although its tail appears to 
be the chief instrument of progressive motion ; for.this p 
the tail, like that of a fish, is alwa tended, and the effect is. 
produced by a vibratory action. 
* Dr. Shaw is of opinion that this insect might be UN to constitute a distinct genus. : 
At all events it appears sufficiently remote from that of Oniscus, and seems more nearly 
allied to some of the smaller divisions of th | Cancer, though not properly belonging. 
to any of them. 
Length 
