THE SLEEP OF MOLLUSKS. 103 



winter tinder projecting rocks high upon the bluffs of the South 

 Platte River. 



In the tropics the process of aestivation is analogous to hiber- 

 nation, but there is not so complete a cessation of the functions. 

 The same epiphragm is made, and the rest is taken for the same 

 purpose to avoid the vicissitudes of climate ; only in this case it 

 is to escape drought instead of cold. And sometimes the same 

 gregarious habit is observed, and the snails crowd in closer than 

 the occupants of a cheap lodging house. On some of the west 

 Florida keys I have seen Helix Carpenteriana aestivating under 

 grass and logs in such vast numbers that one might scoop them 

 up by the quart ; and in the Maritime Alps I have found other 

 species of the land snails piled together by hundreds in hollows 

 of limestone cliffs during the dry season. The strophias either 

 cling to the stems of low bushes or lie at their roots, as do many 

 species of Bulimulus, often in great numbers. 



The arboreal species firmly attach themselves to the bark of 

 the trees on which they live and on whose foliage they subsist, 

 and form a solid epiphragm of the consistence of sole leather.* 

 On the lower part of Florida and on the keys the magnificent 

 OrtJialicus and Liguus, the latter gaudy with bands of yellow, 

 brown, and green, the former a soft cream color, with markings 

 of jet black and brown, live often on such trees as the Jamaica 

 dogwood (Piscidia erythrina) and the Bur sera, which shed wholly 

 or in part their leaves during late winter and spring, the dry sea- 

 son. The sight of one of these trees without foliage, and loaded 

 with this strange, glittering fruit, is enough to thrill the heart 

 and stir the blood of any collector, and I shall never forget my 

 first experience with them at Cape Sable. In my eagerness to 

 possess the beautiful things I broke several specimens, as the epi- 

 phragm adhered so firmly that the shell crushed before it would 

 loosen, and I could only save them by cutting away the bark. 



One wonders why these snails so freely expose themselves dur- 

 ing aestivation, when they are utterly powerless to escape from 

 their enemies. Many of these trees, which were full of them, were 

 isolated more or less and were without foliage, and every shell 

 could be seen hundreds of feet away. That they have enemies I 

 discovered afterward as I wandered broken-hearted among the 

 thick scrub of Key West to find quantities of fresh broken Orthal- 

 icus lying on the ground, but not one alive. Many of them ap- 

 peared as though a hole had been picked in them by birds large 

 enough to get out the snail and utterly ruin the shell. In this 

 case death came swiftly and painlessly, no doubt, while they were 



* The epiphragm of Orthalicus zebra is admirably figured and described by Fischer and 

 Crosse in Mission Scientifique au Mexique et Amerique Centrale. 



