Plate To 



Pisaster ochraa us 



Figure 1. Portion of actinal and lateral skeleton from near base of ray of a medium-sized specimen 

 from Monterey Bay; S, superomarginals; I, inferomarginals; a\ a~>, actinal plates, 

 of which three transseries are shown. The secondary plates are shaded darker than 

 the primaries. The adambulacrals are adjacent t<> the three lowermost, or inner- 

 most, actinals, X8. 



2. Month plates and adoral carina of a medium-sized specimen from Monterey Bay, X8. 



3. Actinal skeleton of a small specimen (R 80 mm.) showing three longiseries of actinal 



plates and the lower-lying plates of the interbrachial septum. The adambulacral 

 plates are shown as a dark band, without detail. 7, inferomarginals; a 1 -^, actinal 

 plates; int., interradial line; Monterey Bay; X8. 



4. Abactinal skeleton of a young specimen (R 20 mm.) from Departure Bay, British Co- 



lumbia, X10. On the left is the central portion of the disk, with the dorsal and 

 lateral skeleton of the proximal part of right half of ray, on right. 'In this speci- 

 men there is one series of well-developed actinal plates, with the second just appear- 

 ing adjacent to adambulacrals; actinal skeleton not shown.) The upper dotted 

 line marks the carinal series (R-R') while the lower indicates the interradial line. 

 B, primary interradial plates, one carrying the madreporite; C, primary central 

 plate; DL, dorsolaterals; /, inferomarginals; .S, superomarginals; ft, primary radial 

 plates. 



5. Forma confertus, Departure Bay, British Columbia; seven abactinal spinelets, 0.85 to 



1.2 mm. in length for comparison with 5a and 5c. 

 5a. Forma ochraceus; three abactinal spines from a Monterey specimen, X10. 

 56. An inferomarginal spine from same specimen. 

 5c. Forma nodiferus, Tongass, Alaska; an abactinal spine, X10. 



6. Pisaster ochraceus segnis forma nodiferus, Laguna Beach, Orange County, Calif.; an 



abactinal spine, X 10. 



330 



