120 



PAXA^IIC DEEP SEA ECHINI. 



encroach largely upon the abactinal plates of the interambulacral areas, 

 Figs. 157, 158 (Pis. 64, figs. 7, 8; 65, figs. 4, 7), and all have a stone canal 

 occupying the greater part of the single central plate of the abactinal system, 

 in which no trace of the separate genitals can be detected. Neolampas (PI. 

 64, figs. 7, S) has but three genital pores ; the left anterior one is atrophied, 

 Fig. 157. In a young Echinolanipas of 4 mm. the central apical plate is well 

 defined when seen from the exterior. The madreporic body is already 

 slightly indicated (PI. 64, fig. o), but there are no traces as yet of any 

 genitals. The stone canal is prominent (PI. 64, fig. 4) seen from the inte- 

 rior of the test. 



10 mm. 



Fig. 157. Neolampas rosteli.ata. 



Fig. 1.58. C'AssiDrr.rs EroKNLfi. 



Attbr Lot^. 



The ocular pores in all the Cassidulids are prominent, and the ocular 

 plates sharply defined (Pis. 64, fig. 7; 65, fig. 7). In Neolampas (PI. 64, 

 fig. 6) there are clusters of four or five spheridia in the ambulacra near the 

 actinal system. In a young Echinolanipas of 4 mm. (PI. 64, fig. S) there was 

 only one on the second row of ambulacra! plates. In Neolampas the 

 spheridia stand out freely from the test, while in Rhynchopygus they are 

 placed in cavities. The abactinal ambulacral plates in this young stage 

 (PI. 64, figs. /,, 5) have but one pore, as in Neolampas (PI. 64, figs. 7, cS'), 

 and not the double pores characteristic of the older Echinolanipas (PI. 65, 

 fig. 4) of Conolampas (PI. 65, fig. 7), and Echinoneus. 



The membrane of the actinal system of Neolampas and of Echinolampas 

 is packed with minute calcareous plates of nearly uniform size. The 

 actinal system of Neolampas is longitudinally elliptical (PI. 64. fig. (>), 

 while that of Echinolampas, Rhynchopygus. and Conolampas is transverse 

 (Pis. 64, fig. ;?; 65, figs. ;?, 6'); Figs. 153-156. 



