18; 



PLATE LXXII. 



Hymeniacidon pibmus, Bowerhanh, 



Fig. 1. — Represents the type-specimeu, in the 

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



Fig. 2. — One of the skeleton spicula. x 260 

 linear. 



Hymeniacidon eadiosa, Boiuerbanh. 



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. 



HYMEmACiDON PLACENTULA, Boiverhanl\ 



Fig. 6. — 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 attenuato-elongo-stellate retentive 

 spiculum from the dermal membrane. X 530 linear. 



Hymeniacidon plumiger, Boiverhank. 



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

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



