b PROCEEDINGS OF THE NATIONAL MUSEUM vol. 121 



Discussion of Species 



Descriptions, synonyms, and illustrations of the species discussed 

 below can be found in Mortensen (1928-1951), and Kier and Grant 

 (1965). 



Eucidaris tribuloides (Lamarck) 



Only one specimen of this species was seen on the Caribbean side: 

 in two feet of water in a crevice between a sponge and rock. Living 

 with it were many individuals of Echinometra lucunter (Linnaeus) 

 and Diadema antillarum Philippi. 



Tripneustes ventricosus (Lamarck) 



Plates 1 (fig. 2), 2 (fig. 4) 



Only three specimens were seen in the Caribbean. Two of them 

 (pi. 2: fig. 4) occurred in just two feet of water on a rock outcrop, 

 one of them up under a rock. The third specimen was in 30 feet of 

 water on sandy, grassy bottom. None of the specimens had any weed 

 or fragments held over its test. Although a thorough search was 

 made for more specimens, none was found. 



On the Atlantic side this species was abundant at Woodford Hill 

 Bay, where they were found in 10 feet of water (pi. 1: fig. 2). Here 

 a few fragments of weed were held over each test. In some places 

 the echinoids occurred in such abundance that their tests were literally 

 touching each other. Lewis (1958, p. 614) reports that in the Bar- 

 bados individuals of this species crowd together on the upper surface 

 of rocks during March and April in order to spawn. Presumably, 

 since it was April when I saw this concentration in Dominica, these 

 individuals also were spawning. 



Echinometra lucunter (Linnaeus) 



This species was found only at a few sites on the Caribbean side, 

 usually restricted to intertidal zones. It was found only where the 

 normal steep gradient of the sea floor was interrupted by a rock out- 

 crop that formed a platform at intertidal depths. Such sites occur 

 at Massacre, Crabiere Point, and Point Ronde. Here the echinoid 

 occurs in great abundance with approximately two to four specimens 

 in every square foot. Normally, the echinoid lives in a hollow that 

 he presumably has formed in the rock. He is associated with many 

 sea anemones and much algae. Many of the echinoids are exposed 

 at low tide to the air. Deeper than eight feet they are rare, with 

 their greatest concentration at one to two feet below low tide. In 



Figure 1. — Coral mass in SO-foot depth at locality 8; the crinoid Comactinia echinoptera 

 (Muller) can be seen living in crevices in the coral. Figure 2. — Tripneustes ventricosus 

 (Lamarck) in 10 feet of water in dense aggregations, presumably to spawn. 



