No. 19.] ECHINODERMS OF CONNECTICUT. IO9 



westward currents from the colder and deeper waters nearer the 

 eastern portion of the Sound. Specimens have been taken near 

 the Thimble Islands and near Faulkner's Island. Off New 

 London and eastward to Waitch Hill, Rhode Island, the individ- 

 uals become increasingly abundant and of larger size. The 

 species also occurs on the northern coasts of Europe, the north 

 coast of Siberia, and on both sides of the northern Pacific 

 Ocean and Bering Sea, southward to Kamchatka on the west 

 and Puget Sound on the east. 



The species prefers rocky bottoms, the food consisting largely 

 of algae growing upon the rocks. Mud containing diatoms and 

 other minute organisms is swallowed in abundance, and any dead 

 animal is greedily devoured. Even the bones of a dead fish will 

 be cut away with the sharp teeth and completely devoured. 



Farther to the north the species lives in great abundance be- 

 tween tides. In the southern part of its range it may reach a 

 depth of more than 600 fathoms. 



Individuals of this species grow to a larger size than do those 

 of the purple urchin, the diameter of the test measuring from 

 two to three inches in large specimens.* The test is rather flat- 

 tened, being about half as high as broad. The spines are ex- 

 ceedingly numerous, but are small and short, the largest being 

 only about a half-inch in length. 



The peristome measures from three-fourths to one inch in 

 diameter, and is proportionally larger in young than in mature 

 individuals. The anal plates are numerous and very small in 

 full-grown specimens. 



The color in life is greenish, varying in shade in different 

 individuals and often on different parts of the body. Many 

 specimens have the zones bearing the tube- feet much lighter in 

 shade than the interambulacral areas. In many there is a yel- 

 low, red, or purple tinge, due to variations in the coloration of 

 the spines; and in some these shades are intensified, the spines 

 being tipped with deep red, purple, or violet. The miliary spines, 

 pedicellariae, and tube-feet are whitish or pale violet. 



The species differs from Arbacia punctulata in that all the 

 plates of the aboral pole bear minute protective spines. The 

 larger spines of the test are longitudinally fluted and pointed at 

 the tip. They are arranged in a double series on each ambulacral 



* Several very large specimens in the Yale University Museum exceed four 

 xncbes in diameter. 



