Some of these Prawns are now living in one of my aquaria. They were taken in a brackish dyke or cut near Newhaven, in Sussex, and in the mud which was brought back with them were a number of small bivalves of the genus _Sphaerium_. Most people know Mr. Kew’s exceedingly interesting book, _The Dispersal of Shells_[44]. In it he relates some extraordinary instances of the way in which species of shells are carried short distances, and may be carried from one district or country to another. These Prawns offered a good illustration of this, and practically confirmed some of the statements in his book, for on several occasions they were seen with the bivalve shells attached to their walking legs. The molluscs lay half buried in the mud and vegetable _débris_ at the bottom of the tank, and as the Prawns walked about they sometimes trod between the open valves, which, as they closed, fastened on to the intruding limb. On one occasion the molluscs did not relax their grasp for days; and had this incident occurred when the creatures were at liberty the molluscs might have been carried for a considerable distance. If specimens of _Sphaerium_ are put into an aquarium containing Prawns of this kind, it is probable that before very long the crustaceans will have one or two attached to some of their limbs. Prawns are exceedingly beautiful, and if we get hold of live specimens, from salt water or fresh, they should be put into an aquarium--the smaller, in reason, the better--so that their motions may be watched with the hand lens. If much weed be put in, the Prawns will use their walking legs in preference, while if there is little vegetation the powerful tail-fan will be employed for motion backwards, while the five pairs of limbs on the abdomen enable their owners to move forwards through the water. From Fig. 66 one may get a good notion of a Prawn, and of the points in which Prawns, in the zoological sense of the word, differ from Shrimps. The head of the Prawn is armed in front with a long blade-like beak, studded along its upper and lower edges with a series of teeth like those of a saw, and the second leg is chelate, that is, armed with pincers, resembling, in miniature, that of a lobster or crab. In the Shrimp, on the contrary, there is scarcely a trace of the beak, and the first leg is incompletely chelate, or sub-chelate[45] (Fig. 67), its last joint folding back upon the one that supports it, just as the blade of a pocket-knife closes on its handle. These two distinctions hold good between all Prawns and all true Shrimps. [Illustration: FIG. 66.--Prawn.]