4 HAWAIIAN AND OTHER PACIFIC ECHIXI. 



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

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

 refnirds as characteristic of the genus Cidaris ; as a matter of fact, how- 

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

 length; the stalks (PI. 2, fig. 2) 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 pedicellarioe fPl. 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 pedicellarioB (PI. 2. fig. 3) 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. The 

 valves are .20-50 mm. in length, wdiile 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 Yal. Agassiz et Desor. 1846, Cat. Eais. Ann. Sci. Xat. (3) VI, p. 326. 



Plate 1, figs, i, 3. 



All three kinds of pedicellaria3 are commonly present, but in specimens 

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

 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 pedicellarinB are like those of C. trUndoides in form, 

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

 about e(juals the liead and may have a well-developed limb, but this is 

 nion^ roininonly lacking (Tl. 1, fig. /). These pedicellariiV occur mainly 

 on tiie abactinal interambulacra. 



The tridentate pedicellariie are siirillar to those of frihidoidrs, but are 

 somewhat larger. They occur mainly on the actinal surface. 



The small globiferous ])edioellari;i^ (PI. 1. fig. :?) are like those of frihu- 

 ioidcs, but are larger, .sometimes .75-. 80 nun. 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. 



