In colour it is greyish brown, clotted all over with dark brown. In this species heat does not improve the colour.
This variety is one of the most abundant of all coast crustacea, swimming about and laying on the sands (which they closely resemble in colour) in immense shoals. Sometimes they are also found in deep water, but the margin of the sea is their favourite habitat. It may be added, that large quantities of the smaller palæmonidæ are caught with and sold as shrimps. Shrimps are in spawn all the year through, and cast their shells during the three months of spring.
The Entomostraca of Milne Edwards, or the Lophyropoda of Latreille, have no suctorial mouth or mandibles capable of mastication; their maxillæ are lamellose, and they have never more than ten swimming feet, and have from one to two eyes on stalks, and live in fresh water. There are two principal genera; the Copepoda of Edwards, and the Ostracoda. As a type of the first, we may mention Cyclops vulgaris (Leach), which, true to its name, has but one eye. But the genus Pontia of the same family has two. As a type of the second order, Ostracoda, we will specify the numerous family of the Cyprides, whose animals are enclosed in a bivalve shell, which causes their remains in Secondary strata to be classed with bivalve molluscs.
CHAPTER XVIII.
FISHES.
Before speaking of the habits of the principal kinds of fishes, it is desirable to glance at their organization, and upon the manner in which they execute their physiological functions.
Fishes are intended to live always[14] in water, and this circumstance has impressed its seal upon their organization. Nevertheless, their forms are very varied; they are generally oblong, compressed laterally. They have no neck, the head being merely a prolongation of the trunk. In the majority of instances, the body is covered with scales, generally a thin bony substance developed out of the skin and overlapping each other, like the tiles of a roof.
Nothing is more remarkable than the variety and brilliancy of colour in fishes; they present almost every gradation, from golden or silver, and other dazzling colours, mingling with shades of blue, green, red, and black.