246 
BRITISH ENTOMOSTRACA. 
the Argulus referred to one species, which seems pretty 
generally diffused over Europe. 
In 1837 Messrs. Herrick and Dana described another 
species in the ‘ American Journal of Science and Arts 5 for 
that year. It was found in Mill River, Whitneyville, prey- 
ing upon the fish called the Sucker, a species of Cato- 
stomus. The description of this species was accompanied 
with most elaborate anatomical details, and illustrated 
with numerous good figures. They gave a very accurate 
description also of the young or imperfect animal. Various 
other notices of the Argulus have been published since 
that. A short account of the common species was inserted 
by Mr. Thompson, of Belfast, in the c Annals and Maga- 
zine of Natural History 5 for 1839, vol. v, with a very in- 
teresting account of the habits of the little creature, as 
observed by himself in an individual taken alive at Belfast, 
and kept by him for some time ; and in the e Memoirs of 
the Helvetic Society 5 for 1845, M. Vogt has given some 
very interesting details of the same species, with good 
figures, illustrative of some parts of its anatomy. A third 
species has been described by Mr. Gould, in his ‘ Inverte- 
brata of New York, 5 under the name of Argulus alostf, and 
more recently, a fourth species has been added to the list 
by M. Lucas. It was found by him in Algeria, and is 
figured in the recent 'Exploration scientifique deTAlgerie. 5 
Anatomy and Physiology , 8fc . — The body of the Argulus 
is covered by a carapace of a greenish hue, and nearly 
transparent. It is slightly convex, obtusely rounded in 
front, and deeply notched behind. This deep notch is 
occupied by the thorax, which at first sight almost escapes 
observation, the animal apparently having the cephalo- 
thoracic portion of the body covered altogether by the 
broad carapace. This may be divided into three parts. The 
first, or anterior, is rounded in front, and prolonged behind, 
terminating in a blunt point. The other two, the posterior 
portions, are of an oval form, and cover the lateral parts 
of the animal. They arise towards the middle of the 
