INSTITUTE OF SCIENCE, PHILADELPHIA. 



protecting shell was very remarkable, but whether this correspondence 

 was in the present instance merely accidental or as the result of selection, 

 I am not prepared to say. That a unity of color between the shell 

 and the crab would in a measure tend to conceal the latter from general 

 observation and thus secure for it a partial protection from its enemies, 

 is undeniably true ; but it may be questioned whether the peculiar 

 tints of the animal were not, in this special instance, a development 

 depending upon the general surroundings the grassy bottom, etc. 

 rather than a relation holding with the shell, the choice and subsequent 

 habitation of which may have been purely fortuitous circumstances. 



The Vermetus " reef" was here again largely developed, forming a 

 prominent fringe along the shore margin. I picked up two stranded 

 jelly-fishes, of the genus Cyanea, which had evidently only quite recently 

 been washed on the beach; the disk of the larger individual measured 22 

 inches in diameter. Both specimens were kept on deck of our schooner 

 for four days, with the object of drying and ultimate preservation ; but 

 at the end of that time, owing to an unfortunate accident, which resulted 

 in their partial destruction, and the steadily growing odor of decompo- 

 sition, I reluctantly heaved them overboard. The elimination of water 

 had been very rapid during the period of desiccation, and in a short time, 

 doubtless, but for the accident, both disks, beautifully exhibiting all the 

 lines of structure, would have been ready for final preservation. 



The bottom of the inlet was in places covered with a species of 

 sea-anemone, one of the forms occurring off Sand Key, in Clearwater 

 Bay, and also with the common sea-urchin (Toxopnciistcs variegatus). 

 The latter had in nearly all cases covered itself with a dome of gravel 

 and broken shell in imitation of the general character of the bottom 

 which was supported on the extremities of the ambulacra! feet, and 

 served to conceal the animal from view. Mr. Willcox had on a previous 

 occasion called attention to this remarkable habit on the part of the 

 urchin, but he seems not to have fully recognized the importance of 

 the deception played by it as a factor in its own defense. So complete 

 was this deception that I must have wandered probably over a full acre 

 of urchin-ground before I was made aware of the presence of these 

 animals ; indeed, were it not for accidentally stumbling over one of the 

 hillocks, thereby exposing the animal beneath, I might to the present 

 time have been left in ignorance of their existence there. To positively 

 test the nature of this covering of broken shell I partially filled my 

 collecting bucket with shell fragments, and placed in it a number of the 

 urchins stripped of their covering. With wonderful rapidity the fright- 

 ened creatures bored their way into the mass of debris, and appeared 

 almost immediately with a large accumulation of shell fragments centred 

 on their ambulacral tips. There could be no doubt, whatever, as to at 



