STRONG YLOCENTROTUS GAIMARDI. 443 



are the proportionally larger size of the two principal vertical rows of 

 ambulacral tubercles, the well-marked scrobicular circle of the primary 

 tubercles of both areas, the proportionally smaller actinostome, and the anal 

 system, which is completely covered by secondary tubercles ; the actinal 

 cuts are less marked, and the ambulacral region broader. 



Actinal surface flattened, generally somewhat depressed from above, regu- 

 larly arched in profile. There are two main vertical rows of very large 

 tubercles, each occupying the larger part of a coronal plate in the interam- 

 bulacral spaces, each flanked by a shorter row of smaller tubercles, uniting 

 on the median line, and an irregular row of tubercles of the same size sepa- 

 rating the principal rows from the poriferous zones. The rest of the plate 

 is loosely filled with secondaries of different sizes, and a few miliaries 

 arranged round the well-defined scrobicular circles of the primaries. In the 

 ambulacral zone the median vertical line is formed of small secondaries, 

 irregularly arranged ; the rows of larger secondaries of the poriferous zone 

 form a vertical line of tubercles of same size. 



No. of Diameter Diameter Diameter Width Length of 



Coron. Plates. Diameter. Height. Act. Syst. Abact Syst. Anal Syst. Poril. Zone. Spines. 



14. 71.3 37. 25.G 14. 8.2 4.8 56. 



18. 117.C 59.1 34.5 22. 10.9 7. 53. 



Formosa ; Puget Sound ; San Diego. 



Strongylocentrotus Gaimardi 



! Echinus Gaimardi I»r... 1825, Dist. Sc. N. O. 



! Slrongi/locenlrolus Gaimardi A. Ag., 1872, Rev. Ech., Pt. I. p. 1G3. 



I am strongly inclined to believe that this species will ultimately prove to 

 be nothing more than S. lividus of the Mediterranean and Azores. Unfortu- 

 nately the material from Brazil is small ; there are but two specimens in the 

 Paris Museum, and we possess but few, — all nearly of the same size, vary- 

 ing from 25 mm to 31 mm ' in diameter. A careful comparison with specimens 

 of S. lividus of the same size shows no differences sufficient to separate them, 

 and which age would not modify to a considerable extent in larger speci- 

 mens. In the Brazilian specimens the spines are slightly stouter, the genital 

 and ocular plates are grooved by radiating lines from the anal system to the 

 outer edge of the plates, — the only feature I have never seen in any of the 

 specimens of S. lividus examined. As the Brazilian specimens are all small, 

 other features may be developed during their growth by which these two 

 species, evidently most closely allied, may be further distinguished; but the 



