50 HAWAIIAN AND OTHER PACIFIC ECHINI. 



The quadridentate pedicellariae (PI. 45, fig. 1) are much less common 

 than the tridentate, and are only known to occur in three species. They 

 are usually found on the actinal part of the interambulacra. The head is 

 shorter than the stalk, sometimes very much so, and there is practically no 

 neck. The valves (Pis. 45, fig. 2 ; 46, figs. 1, 2) range from about three- 

 fourths of a millimeter up to two millimeters in length and are straight and 

 commonly more or less flat. They may afford useful specific characters. 

 Doderlein found one of these pedicellarise viiih.five valves, but we have never 

 seen more than four. 



The ovoid pedicellariffi (PI. 45, fig. 4) are not very common, but are usually 

 to be found on the interambulacra. The head (PI. 45, fig. 18) is about one- 

 fourth of a millimeter long, and is attached to the stalk by a neck of about 

 the same length. The stalk itself is three to six times as long as the head. 

 The three valves (Pis. 45, figs. 5, 12, 23 ; 46, figs. 5, 6) are all alike and are dis- 

 tinctly longer than broad. They commonly lack an " articular loop " on the 

 base, but this is occasionally present. For this reason, they seem to us to 

 be modified ophicephalous pedicellarise, while Doderlein considers them to be 

 small tridentate. They are undoubtedly comparable to the triphyllous 

 pedicellarice of other Echini, but are hardly sufficiently modified to be 

 called by that name. 



The globose pedicellarise (PI. 45, fig, 6) are usually common and often 

 abundant, and are to be found on all parts of the test, though they are most 

 frequent on the ambulacra and about the abactinal system. There are 

 often five groups of them present on the buccal plates in large specimens. 

 The head is about one-fourth of a millimeter in length, and the stalk is 

 usually about the same, though it may be twice as much ; there is no neck. 

 The valves (Pis. 45, figs. 7, 13, 19, 22; 46, fig. 4) are provided with an 

 " articular loop " on the base, but as this is never very large, those of the 

 same head do not differ appreciably from each other. The valves are short 

 and deep, rounded at the tip, and about as wide as long. While there are 

 usually only three, pedicellarise with four such valves are occasionally to be 

 found. In spite of the small size of the articular loop, there is no reason to 

 doubt that these globose pedicellarise of the SalenidiB are ophicephalous. 



The sphferidia of the Salenida3 (Pis. 45, figs. 8, H, 15, 25; 46, fig. 8 ; 

 see also A. Agassiz's Panamic Deep Sea Echini, PI. 19, fig. 2) occur on each 

 ambulacrum, at or near the peristome. There are usually two, sometimes 

 three or even more, rather close together, at the middle of the ambulacrum, 



