46 



PANAMIC DEEP SEA ECHINI. 



resorbed, Fig. 75, and as they become older and the first formed actinal 

 ambulacral plates are more or less resorbed (PI. 20, figs. 2, 3) they become 

 smaller, and the double plates are brought close to the actinostome (PI. 20, 



fig. 4). 



In Salenia hastipera (PI. 20, fig. S) the double plates have the same 

 position as in S. miliaria (PI. 20, fig. 3). In Salenia Pattersoni nearly all the 

 ambulacral plates are double plates and may become so up to the abactinal 

 system. In a specimen 13 mm., Fig. 77, there are intercalated plates above 

 the sixteenth plate, which is a double one. In a specimen of 5 mm., 

 Fig. 76, all eight of the ambulacral plates are double except the youngest 



Salenia Pattersoni 



plate, which on one side is a single, on the other an intercalated plate 

 (PI. 20, fig. '>). Loven has indicated this structure for S. Goesiana by 

 calling attention to the alternate position of the ambulacral pores in the 

 plates nearer the actinal system. 1 



Large tridentate pedicellaria? are found in both the ambulacral and in- 

 terambulacral areas below the ambitus as well as on the actinal system. 

 On the latter round the actinal tentacles are found clustered small short- 

 stemmed pedicellarise. On PI. 19, fig. 2, are figured spheridia at the 

 actinal extremity of the left posterior ambulacrum. 



In a specimen 16 mm. in diameter (PI. 14, figs. 3-5) the coronal plates 

 are 10 mm. in height, the abactinal system rising 4 mm. above that (PI. 14, 

 fig. 5)\ the abactinal system measured 11 mm. across (PI. 17, fig. 3), the 

 greatest width of the anal system being 5 mm. and that of the actinal 

 system 8 mm. in diameter (PI. 19, fig. J). In a specimen 17 mm. in 

 diameter there are seven primary tubercles and five ambulacral plates to 

 each of the largest interambulacral plates (PI. 18, figs. .5, 0). 



1 Loven, Ecbinoidees, PI. XIX, figs. 162, 165. 



