THE SHELLS OP THE GULF OF CALIFORNIA. 209 



repeatedly given by the late Professor E. Forbes to a beginner, 

 "follow your own judgment;" or, as expressed in the phraseology of 

 an American politician, "be sure you are right, then go ahead." 



But let us leave the surface of our Thorn Oyster, and examine what 

 lies hidden in the ponderous substance of the valves. If the outside 

 swarms with life, it is only the portal to the vitality which teems 

 within. We will not speak yet of the worm-eaten passages, the 

 entrances to which often riddle the external surface, making it look 

 like solid sponge, but we will direct attention to certain ominous- 

 looking holes, bearing the same relation to the oyster that the 

 entrance to the great cave does to the State of Kentucky. (We may 

 be allowed to compare small things with great, for in nature all small 

 things are in one sense great; in another, all great things small.) 

 These cavern-mouths are of various shapes, but evidently not irregular. 

 Some of them are always round, others always oval, others 8-shaped. 

 Out of some of the windows, opened but a little way, may be seen 

 protruding a, pair of stony lips, belonging to a mouth so straight in 

 outline that, according to physiognomical diagnosis, its possessor must 

 be of secretive turn of mind. The diagnosis is true. Other mouths 

 protrude from other holes, but with bird-like bills projecting, duck- 

 shaped, as though to gobble the delicate morsels of the sea, or long and 

 twisted, as in an attitude of defiance. But some display neither 

 lips nor beaks; which after all have no connexion with mouths, but 

 rather with noses, as will be presently explained. Let us take our 

 glass, and for once imitate King George III, as described by Peter 

 Pindar, and stare down the vacant, holes "like a magpie peeping into 

 a marrow bone." The wise bird can see nothing but darkness. As 

 the awkward bulk of our bodies precludes our entering the dark 

 chambers of the cave with lighted lamps, we must find other means 

 of exploring the penetralia. Let us set to work like geologists, with 

 hammer and chisel, and not grudge an hour or so in observing how 

 the creatures of a former generation spent their lives, like the Kings 

 of Egypt, in making their own sepulchres. Carefully we remove 

 layer after layer of t\ic oyster shell, and lay bare the underground 

 passage. Its floor and sides and roof are all wrinkled, presenting in 

 miniature the appearances often caused by the running water in the 

 great eaves of this country. It is not water, however, that has so 

 regularly roughened these. And why is it divided all along, like the 

 Thames tunnel, by a stalactitic ridge along the upper surface, almost 

 meeting a similar layer of what might be thought stalagmite rising 

 from below? Suddenly it makes a, turn. We have chiseled through 

 the colored portion of the shell, which we find riddled ami compara- 

 tively soft; now we are on a bed of solid white marble. Indeed, as 

 we try our chisel against it, we find it much harder than marble el- 

 even than the ancient limestone. Life, though it be that of the tender 

 oyster, can build more solid structures than the ocean, with its mighty 

 force of waves. We are obliged to spend some time in chiseling shafts, 

 levelling mounds, and preparing a field of operations to follow the new 

 direction. The bipartite rugose tunnel suddenly widens, and we find 

 ourselves in a spacious cave, beautifully smooth and regular. Its shape 



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