IN THE MUD OF THE LEVANT. 21 



Fig. 25* is a species of Cocconema, separated 

 from its pedicle, which latter character alone 

 seems to distinguish this curious genus from the 

 Naviculse. 



The objects to which I would next direct 

 attention also belong to the disputed domain 

 which appears to link the animal with the vege- 

 table kingdom. They are the spicula of sponges. 

 It has long been known that some sponges have 

 their elastic network strengthened by siliceous 

 and calcareous spicula ; but the number of forms 

 with which naturalists were acquainted was very 

 limited, and indeed mainly referable to two types, 

 the acicular and the tri-radiate, the former being 

 long believed to represent the siliceous, and the 

 latter the calcareous structures. Within the last 

 few years, however, the labours of Mr. Bower- 

 bank and others have led to the discovery of 

 many varieties, alike peculiar and beautiful. 

 Several of these occur in the Levant mud, as 

 might have been expected from the known abund- 

 ance of sponges in the Mediterranean and neigh- 

 bouring seas. 



* The number is accidentally omitted from the figure in the 

 upper corner of Plate II. 



