OF THE SPONGIADjE. 179 



Halyphysema, Bowerbank. 



Sponge. Consisting of a hollow basal mass, from which 

 emanates a single cloacal fistula. Skeleton. Spicula 

 of the base disposed irregularly ; spicula of the fistula 

 disposed principally in lines parallel to the long axis 

 of the sponge, without fasciculation. 



Type, Halyphysema Tumanowiczii, Bowerbank. 



In its form and habit the type of this genus closely re- 

 sembles Polymastia brevis ; but the total absence of fasci- 

 culi in its construction at once marks it as a distinct genus, 

 although a closely allied one. The type species, H. Tuma- 

 nowiczii, is remarkable as being the smallest known British 

 sponge ; it rarely exceeds a line in height. The base of the 

 sponge resembles in form the half of an orange cut at right 

 angles to its axis, and the fistular cloaca is usually dilated at 

 its distal extremity. I have been unable to detect either 

 oscula or pores in any of the numerous specimens I have 

 examined ; but from the general accordance in structure 

 with the genera Alcyoncellum and Polymastia, there is a 

 strong presumption that the oscula will prove to be congre- 

 gated at the distal extremity of the cloacal fistula, as in 

 those genera. 



Fig. 359, Plate XXX, represents a complete specimen of 

 Halyphysema Tumanowiczii, (pronounced Tumanovitchii) 

 based on the stem of a Zoophyte, exhibiting the irregular 

 longitudinal disposition of the skeleton spicula, X 175 

 linear. 



CiocALYPTA, Bowerbank. 



Skeleton. Composed of numerous closed columns, each 

 consisting of a central axis of compact, irregularly 

 elongated, reticulated structure, from the surface of 



