The British species of true star-fishes may be arranged under four families. The _Urasters_ are distinguished from all others by having four rows of suckers in each of the avenues which groove the under surface of their rounded rays. In consequence of the great number of these singular organs, the under surface of a living cross-fish presents a sight truly curious and wonderful. Hundreds of worm-like suckers, extending and contracting, coiling and feeling about, each apparently acting independently of the others, give the idea rather of an assemblage of polypi than of essential parts of _one_ animal. They are sensitive in the extreme, for, if we touch one of those singular tubes when outstretched, all those in its neighbourhood are thrown into a state of agitation; and when it shrinks from our touch, changing from a lengthy fibre to a little shrunk tubercle, some of its neighbours, as if partaking in its fears, contract themselves in like manner. [Illustration: Common Cross-fish.] The common Cross-fish (_Uraster rubens_) abounds on most parts of our shores, so as in some places to be used for manure in large quantities. "It is a sworn enemy to oysters, and as it is frequently found with one or more of its rays broken off, the fishermen fancy that it loses them in consequence of its oyster-hunting propensities; that it insinuates an arm into the incautious oyster's gape, with the intent of whipping out its prey, but that sometimes the apathetic mollusk proves more than a match for its radiate enemy, and closing on him, holds him fast by the proffered finger; whereupon the cross-fish preferring amputation and freedom to captivity and dying of an oyster, like some defeated warrior flings his arms away, glad to purchase the safety of the remaining whole by the reparable loss of a part, as it has the power of reproducing the broken rays. "There is, however, reason to think that the cross-fish destroys his prey in a very different manner from that just narrated; for star-fishes are not unfrequently found feeding on shell-fish, enfolding their prey within their arms, and seeming to suck it out of its shell with their mouths, pouting out the lobes of the stomach, which they are able to project in the manner of a proboscis. Possibly the stomach secretes an acrid and poisonous fluid, which, by paralysing the shell-fish, opens the way to its soft and fleshy parts."--_Forbes's Star Fishes._ The _Solasters_ are "suns in the system of sea-stars," and are entitled to this distinguished rank among the marine constellations by their many rays and brilliant hues. The _Solaster papposa_, or common Sun-star, with rays varying in number from twelve to fifteen, is one of the commonest, and at the same time handsomest, of all the British species. Sometimes the whole upper surface is deep purple, and frequently the disk is red, and the rays white tipped with red. It grows to a considerable size, having been found eleven inches broad.