ORDER ISOPODA— ASELLUS. 49 
This apparently insignificant and minute animal is capable of great injury to wood exposed 
to salt water. It attacks in countless numbers the piers of bridges, wooden wharves, and all 
submerged timber, piercing it in every direction, and soon rendering it useless. It has been 
computed that a stick of timber exposed to these animals, where they are abundant, will lose 
an inch of its diameter annually. They act chiefly below low-water mark. The best mode 
of protection yet discovered is a coat of verdigris, or of metallic copper. The same purpose 
is effected by covering the whole surface with broad-headed copper nails. This animal 
attacks in preference pine and other soft woods, although none, except perhaps live oak, is 
exempted from its ravages. Its injuries are very partially counterbalanced by its benefits in 
destroying sunken timber, or vessels, which might obstruct channels or tideways. 
GENUS ASELLUS. Geoffroy. 
Body oblong, depressed. Head distinct. Segments transverse, crustaceous. ‘Tail of a single 
segment, with two bifid appendices. Feet fourteen. Four apparent antenne, setaceous, 
unequal ; the two superior much shorter, four-jointed ; the two lower much longer, of five 
joints. Several pairs of jaws. Eyes two, simple, sessile. 
ASELLUS COMMUNIS. 
Asellus communis. Say, Journ, Acad. Nat. Sciences, Vol. 1, p. 427. 
Description. Segments transverse, subequal, indistinctly emarginate on the lateral edges, 
furnished with short rigid hairs. Head narrower than the first segment, and not longer. Eyes 
obovate, oblique, black, prominent. Inferior antennz equal to the peduncle of the superior 
ones, which latter extend to the base of the tail. ‘Tail as broad as the segments of the body, 
and equal to the two preceding ones united. Appendices as long as the tail; lacinie sub- 
equal, peduncle dilated. Anterior feet monodactyle, unarmed ; thumb as long as the hand. 
Hand oval; carpus triangular, remaining gradually longer to the hind pair. 
Length, 0.25. Breadth, 0-09. 
This is a very common species in our freshwater streams, and usually found under stones 
and bits of wood. ‘The female is distinguished by a valvular follicle beneath, covering the 
young. 
Fauna — Parr 6*. Li 
