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PLATE LXXII. 



HYMENIACIDON FIRMUS, Boiverbank. 



Fig. 1. Represents the type -specimen, in the 

 cabinet of the Rev. A. M. Norman. Natural size. 



Fig. 2. One of the skeleton spicula. X 250 

 linear. 



HYMENIACIDON EADIOSA, Bowerbank. 



Fig. 3. Represents the type-specimen, in the cabinet 

 of the Rev. A. M. Norman. Natural size. 



Fig. 4. An average-sized skeleton spiculum. 

 X 250 linear. 



HYMENIACIDON PLACENTULA, Bowerbarik. 



Fig. 5. Represents the type-specimen of the species. 

 Natural size. 



Fig. 6. A skeleton spiculum. X 80 linear. This 

 figure also represents the large acerate tension spicula 

 of the dermis. 



Fig. 7. A large equi-angulated spiculated triradiate 

 spiculum from the dermis. X 123 linear. 



Fig. 8. One of the inflato-acerate, incipiently tuber - 

 culated tension spicula of the dermal membrane. 

 X 530 linear. 



Fig. 9. An atteuuato-elongo-stellate retentive 

 spiculum from the dermal membrane. X 530 linear. 



HYMENIACIDON PLUMIGER, Bowerbank, 



Fig. 10. Represents the type-specimen, in the 

 cabinet of Mr. W. Saville Kent. Natural size. 



