STRONGYLOCENTROTUS PURPURATUS. 449 



Strongylocentrotus purpuratus 



! Echinus purpuratus Stimps. 1857, Crust, Echin. Pacif. Coast. 



I Strongylocentrotus purpuratus A. Agass., 1872, Rev. Ech., Pt. I. p. 165. 



PL V.f. 5-e; PL VI. f. 7 ; Pi XXXVI. f. 9. 



Test more gibbous than that of S. albus, to which it is closely allied, with 

 proportionally wider anibulacral area, and test less crowded with tubercles ; 

 primary vertical row not as prominent as in S. albus, and coronal plates 

 higher. The actinostome is also very much smaller in S. albus than in this 

 species, and the tubercles separating the arcs of the poriferous zone, which 

 form lateral rows, are much smaller than in the Chili species. The color of 

 the test and spines is a brilliant violet when alive ; test denuded, when dry, 

 is greenish. 



Coronal plates high ; interainbulacral space with six irregular vertical rows 

 of large tubercles, the rows next but one to the poriferous zone the largest. 

 Scrobicular circle large, tubercles not prominent, miliaries and secondaries fill- 

 ing the rest of the coronal plates not very closely crowded. The secondaries 

 are large, scarcely inferior in size to the primaries. The principal vertical 

 row of primary tubercles of the ambulacra] space is nearly as large as those 

 of the median interainbulacral space. The median ambulacral space is filled 

 by irregular vertical rows of secondaries. The tubercles of the lateral rows 

 of secondaries separating the arcs of pores are larger nearer the inner edge. 

 The abactinal system is distinguished b} r its small anal system, flanked by 

 large ocular plates, two of which reach the anal system. The plates of 

 abactinal system are sparsely tuberculated ; genital madreporic plate pentag- 

 onal, pointed, and very prominent, much larger than the other genital plates. 



San Francisco; Pup-et Sound. 



Strongylocentrotus tuberculatus 



! Echinus tuberculatus Lam., 1816, An. s. Vert. 

 Strongylocentrotus tuberculatus Br., 1835, Prod. 



PL V\f. 4-5; PL XXXVI. f. 4. 



The test is regularly arched, often somewhat flattened ; the spines large, 

 stout, sharp at extremity, and long compared to the size of the test. Anal 



