Boone, Echinodermata, Cruises of "Eagle" and "Ara" 1921-28 127 



These primaries are larger just beyond the base and thence diminish 

 slightly distally; the apex being dilated and obtusely blunt. They 

 are covered with coarse, rounded tubercles set in clearly defined longi- 

 tudinal series which converge on the tip of the spine. The secondary 

 spines are laterally compressed, flat, covered by microscopic longi- 

 tudinal lines and with the apex truncated, slightly rounded. In 

 thouarsii the genital plates form a regular five-rayed star which is 

 much more distinct than in E. tribuloides. 



In the Galapagos specimens before me, the large, globiferous pedi- 

 cellariae are almost entirely lacking; only five being discovered after 

 most careful observation. These were similar to, but relatively larger, 

 than those of E. tribuloides. The small globiferous pedicellariae were 

 abundant on the actinostome, ambulacra, interambulacra and abac- 

 tinal system. They were similar to, but somewhat larger, than those 

 of tribuloides. The tridentate pedicellariae of thouarsii were found 

 sparsely on the actinal surface. They also are similar to, but dis- 

 tinctly larger, than those of tribuloides. 



The largest "Ara" specimen measures 63.5 mm. test diameter. 

 One in the collection of the American Museum of Natural History 

 from Galapagos has a test diameter of 68 mm. 



References : Cidaris thouarsii Valentin, in Agassiz and DeSor, Ann. 

 Sci. Nat., vol. 6, p. 326, 1846. 



Eucidaris thouarsii Doderlein, Jap. Seeigel, p. 42, 1887. ; Bull. Amer. 

 Mus. Nat. Hist., vol. 32, p. 220, 1913.— Mortensen, Studies De- 

 velopment and Larval Forms of Echinoderms, p. 23, pi. V, 

 figs. 1-2 (larval stages), 1921 (Copenhagen). — Boone, Bull. 

 Bingham Oceanog. Coll., vol. II, art. 6, p. 8, pi. 5, lower figure, 

 1928. 



Cidaris thouarsii A. Agassiz and H. L. Clark, Mem. Mus. Comp. 

 Zool., XXXIV, no. 1, p. 5, pi. 1, figs. 1, 2, 1907. 



Eucidaris tribuloides (Lamarck). 



Plate 82. 



Type: Lamarck's type came from the "Indian Ocean" and was 

 originally deposited in the Jardin des Plantes, later placed in the 

 Paris Museum. 



Distribution: Littoral to 120 fms., especially abundant as a reef- 

 dwelling species. Found from South Carolina southward throughout 



