4 HAWAIIAN AND OTHER PACIFIC ECHINI. 



The blade is somewhat curved, so that it has been described as "projecting 

 in a snout-like way." This is the type of pedicellaria whicli Mortensen 

 regards as characteristic of the genus Cidaris ; as a matter of fact, liow- 

 ever, it occurs in several other genera. The valves are .60-.70 mm. in 

 length; the stalks (PI. 2, fig. ,"?) are .60-1.50 mm. long and have no limb. 

 They occur chiefly on the interambulacra and most commonly on the 

 abactinal surface. 



The tridentate pedicellarite (PI. 2, fig. 4) are not specially peculiar. 

 The valves are narrow and somewhat compressed, usually .50 mm. long or 

 less, often much less, but sometimes are nearly or quite 1 mm. ; the stalks 

 are shorter than the valves. They occur almost wholly on the actinal 

 side of the test and are most abundant on the interambulacra. 



The small globiferous pedicellaria^ (PI. 2. fig. S) have a conspicuous end- 

 tooth on each valve ; the opening is not terminal nor is the blade curved, so 

 that the general appearance is quite different from the large ones. Tlie 

 valves are .20-50 mm. in length, while the stalk is from one to three times 

 as long. They occur everywhere on the actinostome, ambulacra, interam- 

 bulacra and abactinal system. 



Cidaris Thouarsii Val. 



Cidaris Thouarsii Val. Agassiz et Desor. 184(), Cat. Rais. Ann. Sci. Nafc. (3) VI, p. 32G. 



Plate 1, figs. 1, 3. 



All three kinds of pedicellariaj are commonly present, but in specimens 

 from the Galapagos Islands and occasionally in those from Panama, tlie 

 tridentate are wholly wanting. The large globiferous are also often 

 reduced in numbers so that only two or three are to be found. 



The large globiferous pedicellarite are like those of C. iribuloides in ionn, 

 but are generally larger, often with valves nearly 1 mm. long. The stalk 

 about equals the head and may have a well-developed limb, but this is 

 more commonly lacking (PI. 1, fig. l). These pedicellaria; occur mainly 

 on the abactinal interambulacra. 



The tridentate pedicellarite are similar to those of irlhuloidcs, but are 

 somewhat larger. They occur mainly on the actinal surface. 



The small globiferous pedicellaria3 (PI. 1, fig. ,?) are like those of iribu- 

 loides, but are larger, sometimes .75-.80 mm. in length of valves, though 

 they are usually under .50 mm. ; the stalk is one to three times as long 

 as the valves. They occur abundantly everywhere. 



