SALENIA MILIARIS. 



43 



Fig. 68, we find seven and nine (PI. 18, fig. 2); and in one of 13 mm., 

 Fig. 69 (PL 18, fig. i) there are seven and ten, new niiliaries being formed 

 in the upper angles of the plates. 



The small size of the auricles of Salenia and other genera is undoubtedly 

 due to the fact that in Salenia and others the coronal plates supply but 

 little calcareous material to the actinal system owing to its relative constant 

 size, and the primordial plate having been resorbed, little or no fresh cal- 

 careous material is added to the actinal plates for their growth. 



The primary ambulacral tubercles are small, placed near the median line, 

 and in older specimens they are separated by miliaries which separate the 

 two vertical rows (PL 20, figs. 3, 4) ; they, however, have the same Hemi- 



5 mm. 



Fig. 70. Salenia vakispina. 



cidaris arrangement which has been observed in other species of the genus, 

 tapering gradually (PL 18, figs. 1, 3, S), Fig. 70, and stopping abruptly at 

 the fourth or fifth plate, where they are followed by large miliaries or small 



