S6 Pub. Puget Sound Biol. Sta. Vol. 2, No. 33 



bulacral pores in rows of 8 or 9 pairs, curving toward the oral region. — 

 Numerous, below the tide line. 



2. Strongylocentrotus drobachiensis O. F. Miiller. Green sea urchin 



Mediumly large, greenish, with tube feet whitish or violet; spines 

 many, all over test, varying in length, 5 to 15 nun., the smallest ones vei'v 

 slender; the largest spines solid, fluted, pointed. Test somewhat flattened; 

 apical plates many, all bearing minute }jrotective spines ; genital plates 

 larger than radials. Pedicellariae many. — Numerous, below tide line. 



3. Strongylocentrotus purpuratus Stimpson. Small purple urchin 



Mediumly large, purple, with tube-feet also purple. Spines numerous 

 all over test, varying in length, 4 to 16 mm., the smallest ones slender; 

 the largest spines solid, fluted, with truncated tips, thicker than those of 

 S. drobachiensis. Test flattened; apical plates many, all bearing spines; 

 genital plates not noticeably larger than radials. — Not numerous, along 

 shore. 



ORDER CLYPEASTROIDA 



Genus Echinarachnius Sea cakes, Sand dollars 



Divisions of dorsal star petal-like with open ends ; furrows on lower 

 side bifurcated and branched ; genital pores 4, none in the posterior inter- 

 radius. 



1. Echinarachnius excentricus Eschscholtz. 



Disk somewhat straight across the posterior part; posterior ambulacral 

 zones shorter than the other three. — Numerous, in sand at False Bay. 



Class Holothuroidea Sea Cucumbers 



KEY TO ORDERS 



A. Tube-feet present. Pedata (p. 38) 



A A. Tube feet none. Apod a (p. 41) 



