EURYCERCUS. 
123 
a species of fresh- water Nais, which he calls the Lurco. 
“So great is the voracity/' he says,* “of this creature, that 
I have seen a middle-sized one devour seven Lyncei in 
half an hour. Five of these were moving about in the 
first cavity, at the end of that time the other two, having 
passed into the second, had become exhausted/'f 
This family contains seven British genera. 
1. Eurycerctjs. — Subquadrangular ; abdomen very 
broad, in form of a flat plate, densely serrated. 
2. Chydorus.— Nearly spherical in shape ; beak very 
long and sharp, curved almost into the shape of a crescent; 
inferior antennae very short. 
3. Camptocerus. — Ovoid -shaped ; abdomen long, 
slender, and extremely flexible ; serrated. 
4. Acroperus. — Shell somewhat harp-shaped, termi- 
nating interiorly on the anterior margin in a more or less 
blunt point projecting forwards ; inferior antennae rather 
long. 
5. Alona. — Shell quadrangular, striated or grooved 
longitudinally ; inferior antennae short. 
6. Pleuroxus. — Anterior margin prominent on the 
upper portion ; the lower part being truncated, or, as it 
were, cut sharp and straight ; first pair of feet very large. 
7. Peracantha. — Oval-shaped ; lower extremity of 
shell slightly curved backwards, and, as well as upper 
extremity of the anterior margin, beset with strong, 
hooked spines. 
Genus 1 — Eurycercus4 
Lynceus, Muller , et auctorum . 
Eurycercus, Baird , Ann. Mag. Nat. Hist, ii ; Trans. Berw. Nat. Club, ii. 
Character . — Subquadrangular. Abdomen very broad, 
in form of a flat plate, densely serrated. Beak blunt, 
slightly curved downwards. 
* Pritchard’s Micros. Cab , p. 81. 
f Vide supra, p. 9. 
X From evpvQ, broad ; and KspKog, a tail. 
