314- A MONOGRAPH OF THE 



This small and often palmate species is figured in 

 plate ii, figs. 2 and 3, in Dr. Johnston's ' History of the 

 British Sponges,' as a small variety of Halicliondria palmata, 

 but it differs materially in its structure from that species. 

 In its general form and habit it has much the appearance of 

 very small specimens of Chalina oculata when both species 

 are in a dried state ; and the delusion may still exist if 

 examined in water only, as the lines of the skeleton are 

 frequently so thickly coated with sarcode as to simulate 

 the cylindrical keratose fibres of a Chalina, and the mistake 

 is further favoured by the spicula within being completely 

 hidden by the surrounding sarcode ; in other specimens, 

 where the casing of sarcode is not so thick, their true cha- 

 racter is more apparent, but a preparation of a section at 

 right angles to the axis of the sponge immediately dissipates 

 the illusion, and all the false appearances of keratose fibre 

 disappear. I have seen a considerable number of speci- 

 mens of this species. They rarely exceed two and a half 

 inches in height. The pedicel is slender and about half an 

 inch in height, and it rises from a thin spreading base. 

 The branching appears to be always laterally, and oscula 

 rarely occur excepting on the edges or terminations of 

 the branches. The dermal membrane in the specimens in 

 my possession has been nearly all destroyed by maceration 

 in fresh water. I examined the small remainder of it, but 

 could not detect any spicula in it. In the interstitial mem- 

 branes, they appear to have been very few in number. I 

 am indebted to my friend Mr. Bean of Scarborough, for my 

 knowledge of this species, and for several very characteristic 

 specimens of it. 



27. Isodictya ramusculus, Bowerbank. 



Sponge. Branching. Surface smooth and even. Oscula 

 prominently elevated, very large, few in number. 

 Pores inconspicuous. Dermal membrane aspiculous. 

 Skeleton. Unispiculous ; spicula subfusiformi acerate, 



