Chap. i. I LITTORAL FAUNA. II 



a geological point of view, as supplying a large part of the 

 material of which calcareous reefs and sand rocks are built up. 

 At St. Thomas the Siphonaceas are especially abundant, where- 

 as at other places, as at St. Vincent, Cape Verde Islands, the 

 Corallinacece appear to supply most of the calcareous matter 

 separated from the sea water by plants. 



The rise and fall of the tide at St. Thomas is only about a 

 foot ; yet along the very margin of the water I found plenty of 

 animals living, some of them only just awash. Sea urchins 

 {Diadema antiUarnni), with extremely long sharp spines, were 

 very common. The spines penetrate a bather's foot or hand 

 with the greatest facility, and breaking off leave a very un- 

 pleasant wound. In gathering specimens I got wounded in 

 the finger, though I took great care ; so well are the animals 

 protected. The animals keep their long spines in constant 

 motion, so that it is very difiicult to avoid being pricked if one 

 tries to handle one. The wound produced by the spines is 

 apt to fester, but there appears to be no poison on the spine. 

 In the case, however, of another genus of sea urchins which 

 I dredged in abundance in shallow water on the Philippine 

 coast, and in which the short spines are hollow and tubular at 

 their extremities, a definite poison certainly exists. Probably 

 there is a poison gland in the tube. A sharp stinging pain, 

 like that produced by the sting of a wasp, but not quite so 

 intense, is felt at the instant when one of these spines pierces 

 the flesh, and the pain lasts for about five minutes. These 

 urchins are peculiar, because they have a perfectly flexible test 

 or shell, and are, I believe, of the genus Asthenosonia (Grube). 

 Allied forms are common in great depths, but in these I never 

 experienced so marked a stinging effect as in the case of the 

 shallow-water ones. 



Large Chitons, three inches in length, were abundant along 

 the shore of St. Thomas, and a very large Annelid, with glisten- 

 ing yellow setfe {Eunice), was a constant feature about the 

 water's edge, crawling over the rocks. In dredging in shallow 

 water most of the seaweeds obtained were of a brilliant green 

 colour,* and amongst these lived a crab and a Squilla which 

 were of exactly the same shade of green, evidently for protec- 

 tion and concealment. 



There is only one kind of Humming-bird at St. Thomas. 

 It is very common, and constantly to be seen hanging poised 

 in the air in front of a blossom, or darting across the roads. It 

 is remarkable how closely Humming-birds resemble in their 

 flight that of Sphinx moths, such as our common Humming- 



* Vdotea cyalhifoniiis, U. conghitinata, and U. flabrllaln, and others, 



