22 



Pub. Puget Sound Biol. Sta. 



Vol. 2, No. 



Class Asteroidea 



KEY TO ORDERS 



A. Ambulacral feet usually in 4 rows ; pedicellariae either forceps-like 

 or shears-like. forcipulata (p. 22) 



AA. Ambulacral feet in 2 rows ; pedicellariae not as above. 



B. Marginal plates small, sometimes indistinct ; margin of animal never 

 rigid. SPINULOSA (p. 28) 



BB. Marginal plates large; margin of animal rigid. 



PHANEROZONA (p. 31) 



Fig. 29. Major pedicellaria of Pisaster ochraceus. X 36. 



Fig. 30. Minor pedicellaria of Orthasterias forreri forciplata. X 36. 



Fig. 31. Minor pedicellaria of Pisaster ochraceus. X 36. 



Fig. 32. Minor pedicellaria of Orthasterias forreri forcipulata. X 36. 



Fig. 33. Small major pedicellaria of Orthasterias forreri forcipulata. X36. 



Fig. 34. Diagram showing the groups of spines used in classification ; 

 (d) dorsal region; (u) upper marginal region; (1) lower mar- 

 ginal region; (i) interactinal region; (a) ambulacral region. X 36. 



ORDER FORCIPULATA (Forcipulosa) 

 Family ASTERIIDAE 



KEY TO GENERA 



A. Rays 5 (rarely 6). 



B. Dorsal spines forming a network or clustered. 

 C. Interactinal spines in 3 or 5 or more rows. 



D. Adambulacral spines 1 row, 1 spine to a plate. 



PISASTER (p. 23) 



