OF THE SPONGIAD^l. 247 



PIG. 



112. TRENCHANT CONTORT BIHAMATE. Shewing the cylin- 



drical form of the shaft at the curves of the hooks, 

 and the middle of the spiculum, and the trenchant 

 edges of the remainder of its inner surface. X 

 400 linear. Hymedesmia JoJmsoni, Bowerbank, 

 MS. From Madeira, Pages 35, 127. 



113. ABBREVIATED BIHAMATE. From an unknown sponge. 



X 1060 linear. I have found but very few speci- 

 mens of this form, and in no case in situ ; and I 

 am therefore in doubt whether it be an adult 

 spiculum, or merely a variety arising from an 

 arrest of development. 



114. DEFLECTED BIHAMATE. When the hami are both 



deflected in the same direction at nearly right 

 angles to the plane of the shaft. From Farrea 

 occa, Bowerbank, MS. The sponge is at the base 

 of Eu/plectella ciicumer, Owen. X 660 linear. 



115. EXTER-UMBONATE BIHAMATE. When the limbo is on 



the middle of the outer curve of the shaft ; from an 

 undescribed sponge from Sicily. X 1060 linear, 

 Page 45. 



116. INTER-UMBONATE BIHAMATE. When the umbo is on 



the middle of the inner curve of the shaft ; from the 

 same sponge as Fig. 115. X 1060 linear. Page 

 45. 



117. BI-UMBONATE BIHAMATE. When the middle of both 



the inner and outer curve of the shaft have an 

 umbo. From the same sponge as Fig. 115. X 

 1060 linear. Page 45. 



118. UNICLAVATE BIHAMATE. I believe to be an arrest of 



development rather than a separate form ; for 

 although I found many specimens of it intermixed 

 with the biclavate forms, I also found others 

 assuming transitional forms, that appeared ulti- 

 mately to connect it with the biclavate spicula. 

 X 1060 linear. Page 44. 



