PLATE XVI. 

 " IsoDiCTTA iNiBQUALis, Bowerbanh. 



Fig. 1. — Eepresents the type -specimen. Natural 

 size. 



Fig. 2. — One of tlie subfusiformi-acerate tension 

 spicula. X 400 linear. 



Fig. 3. — One of the short attenuato-acerate tension 

 spicula. X 400 Unear. 



Fig. 4. — A bidentate, equi-anchorate, retentive 

 spiculum. X 666 linear. 



Fig. 5. — One of the bihamate retentive spicula. 

 X 666 linear. 



Fig. 6. — A subfusiformi-acuate basally and apically 

 spinous skeleton spiculum. X 400 linear." 



" IsoDiOTTA iMPLiciTA, Bowerbank. 



Fig. 7. — Represents the type-specimen immersed 

 amid the branches of Nullipora polymorpha. Natural 

 size. 



Figs. 8. and 9. — Two of the smaller specimens of the 

 species. Natural size. 



Fig. 10. — A small portion of the subfasciculate 

 dermal membrane exhibiting the irregular mode of the 

 disposition of the tension spicula. X 308 hnear. 



Fig. 11. — One of the slender attenuato-acuate 

 tension spicula, basally incipiently spinous, of the 

 dermal membrane. X 400 hnear. 



Fig. 12. — One of the stout attenuato-acuate basally 

 spinous spicula of the dermal membrane. X 400 

 linear. This figure also represents the skeleton 

 spicula. 



Fig. 13. — Eepresents two of the bipocillate anchorate 

 retentive spicula of the dermal membrane. X 1166 

 hnear. 



Fig. 14. — One of the minute inequi-anchorate reten- 

 ,tive spicula. X 1166 hnear." 



