The curious structure of the auriform antennae of this genus, 
agreeing considerably with those of Parnus figured in the next 
plate, induced Latreille to form them into a family which he 
called Otiophori , in his Genera Crustaceorum , &c. ; but he 
subsequently brought back Gyrinus to follow the Dyticidce , 
and left Parnus with his Byrrhii. Gyllenhal, following La- 
treille, placed these genera also together. Mr. W. S. MacLeay, 
in the first part of Annulosa Javanica , having noticed La- 
treille’s error in placing them together, — thereby, as he justly 
says, “confounding a relation of analogy with one of affinity,” — 
I have thought it a good opportunity of introducing these ge- 
nera together, to prove that there is no affinity beyond the 
Linnean system, that of the antennae, the form of the legs and 
the structure of the mouth being totally different. 
The Gyrini live in society, and many of them are extremely 
common in our ditches and rivers the whole of the spring and 
summer, where they must have attracted the notice of every 
lover of nature, by the rapid and curious evolutions which 
they perform during fine weather upon the face of the water 
(from whence their English name of Whirl-wigs), diving below 
the surface when alarmed, and carrying down with them a 
bubble of air appearing like quicksilver, as has been remarked 
by Fabricius. In dull and cold weather they secrete them- 
selves under the banks, or at the bottom of the water : most 
of them have a fetid smell. 
The following species have been detected in this country, viz. 
1. G. seneus Leacli. 
2. marinus Gyll. 
3 . minutus Fab. — bicolor Oliv. — Kirbii Marsh. 
4. Natator Linn. 
5. bicolor Fab. — elongatus Marsh. 
6. villosus Fab. — Modeeri Marsh. 
It is likely that this last species will be formed into a genus, 
as the convex form, villose and punctured surface, and pro- 
jecting labrum indicate a different economy : indeed I suspect 
that this species is not gregarious. 
The plant figured is Parnassia palustris (Grass of Par- 
nassus). 
