110 PLATE XLIV. 



Fig. 19. A bidentate equiangulated retentive spicu- 

 lum from the dermal membrane. X 530 linear. 



Fig. 20. One of the attenuato-acnate, basally and 

 medially-spined, skeleton spicula. X 250 linear. 



Fig. 21. An attenuato-acuate, entirely-spined, in- 

 ternal, defensive spiculum. X 250 linear. 



