Handbook of Paleontology 149 



some species occur in deep water, Sand Dollars and Cake 

 Urchins are found mainly in sand considerably below the 

 low-water mark. Some species thrive when they are sub- 

 ject to the exposure of open sandy beaches. The Green- 

 ish Blue Cake Urchin (Mellita testiidinalis) is very abun- 

 dant in shallow water from Cape Hatteras southward 

 and is even found as far north as Cape Cod. The Heart 

 Urchins found along our eastern coast are yellowish 

 white or brown in color. One species (Schizaster fra- 

 gilis) is one and a half by two inches in size, one inch 

 thick and brown in color, and lives in deep waters. In 

 the warmer waters of the California coast, those of 

 Florida, the Gulf of Mexico and West Indies, there are 

 species of reddish or reddish gray color. The Heart 

 Urchins have heart-shaped, or thick elliptical bodies. 

 There are a few littoral species, but most of them bury 

 themselves in sand or mud and live in deep water. The 

 Stinging Urchin (Diadema setosum) is abundant along 

 the Florida coast and in the West Indies. It is seen in 

 clusters on sandy bottoms and is also found on the reefs. 

 It is a velvety, jet-black in color, grows to four inches in 

 diameter and has sharp-pointed, black spines up to four 

 inches in length which penetrate the skin if seized and 

 break off, inflicting a painful sting. The Brittle Sea 

 Cucumber (Synapta inhaerens) is to be looked for on 

 both sandy and muddy beaches from the Carolinas to 

 Cape Cod and also on the coasts of Europe. It lives in 

 sand tubes. At first sight it looks like a worm. It is 

 translucent with five white lines extending down the 

 length of the body which is highly contractile, but which 

 extended has a length of a foot and a diameter of an 

 eighth of an inch. Under unfavorable conditions it can 

 break itself to pieces by muscular contraction. 



