402 ARBACIA PUNCTULATA. 



short, flanked externally by a line of longer spines next to poriferous zone. 

 Immediately round ambitus the spines are longer; the general coloring of 

 spines and test is dark violet. Dried tests are usually light violet or brownish- 

 yellow, with purple patches in median interambulacral space. This sea- 

 urchin appears to be the most common species of the western coast of South 

 America, As I have shown in A. punctulata, it is not natural to separate A. 

 nigra and A. pustulosa from the other species of the genus, on account of 

 the greater number of the primary tubercles; the only other difference in 

 A. nigra which would be considered generic — the position of the ocular 

 plates — isnotalone sufficient to withdraw it from the present association. 



Arbacia punctulata 



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

 ! Arbacia punctulata Gbat, 1885, Proc. Zool. Soc. London. 

 (See Part II. p. JC3.) 



PI. II f. 4; PI. V.f. l-is; PI- VI- f. .*.■; PI. XXVI. f. 3-7; PI XXXV. 



f.s; PI. XXXVIII. f. 10. 



Long Island Sound ; West Florida. 



Arbacia pustulosa 



I ' 'it/arts pustulosa Lf.ske, i 7 7S, Klein, Add. 



! Arbacia j> ustidosa Gray, 1885, Proc. Zool. Soc. London. 



PI. P. f. 5; PI. IP. f. 15-33; PL V. f. 19-21 ; PI. XXVIII. f. 0; PI. 



[xxxviii f. ur: 



This species is remarkable for the narrow ring of genital plates forming 

 the abactinal system; the elongate anal system; the narrow coronal plates, 

 completely crowded by closely packed tubercles, arranged parallel to the su- 

 tures, of uniform size, with as many as seven to eight tubercles in each hori- 

 zontal row on the sides of the median line. There is no tendency in the tuber- 

 cles to a vertical arrangement in older specimens, they simply form irregular 

 vertical lines ; while in younger specimens the vertical arrangement is mod- 

 erately apparent, The spines are more slender and shorter than in A. punc- 

 tulata. The actinostome is also proportionally larger than in the American 



