COMMON OBJECTS OF THE SHORE. 305 



is most curiously constructed. It is an orifice 

 surrounded by a fleshy ring, and set with little 

 teeth so sharp, and jaws acted upon by muscles so 

 powerful, that it can bite through very hard sub- 

 stances. The whole structure of these sea-urchins 

 is truly wonderful. The description given by 

 Professor Kymer Jones of the shelly case, is most 

 simple and striking. " The crust of the Echinus," 

 observes this writer, " when denuded of its spines 

 or stripped of its external covering, would seem to 

 be an ordinary shell, having its outer surface 

 covered over with polished tubercles, regularly 

 arranged. Of these the largest are disposed in 

 lines that pass from pole to pole of the round box, 

 like lines of longitude on the globe of the geogra- 

 pher. Intermixed among the larger tubercles, are 

 seen innumerable smaller eminences of similar 

 construction, but dispersed with less precise 

 arrangement, upon all of which, when in a living 

 state, spines were attached in correspondent num- 

 ber. Moreover, placed at intervals between the 

 spine-crowned tubercles, are ten broad bands 

 disposed in pairs, all pierced with countless holes : 

 these too extend from pole to pole of the round 

 box, and through them, during life, the locomotive 

 suckers passed, used for climbing rocks and for 

 attachment to some foreign body. On cutting 

 through the shell so far as to see its inner surface, 

 we perceive, to our surprise, that far from being, 

 as it appears externally, a simple shelly exudation 

 moulded to the form of the Echinus, like the shells 

 of lobsters or mollusca, it is a very complex fabric, 

 built with most consummate art, consisting of 

 some thousand pieces, varying in size but shaped 

 with mathematical precision, and composed with 



