VI l] CODIUM. 159 



of the rock and they are not confined to the lines of bedding ; in 

 none of the examples is there any trace of carbonaceous matter 

 in association with the deep moulds. On the whole, then, this 

 Kimeridge fossil cannot, I believe, be accepted as an authentic 

 example of a Mesozoic Gaulerpa. 



It is not improbable that some of the supposed fossil algae 

 may be casts of egg-cases or spawn-clusters of animals. In 

 Ellis' Natural History of the Corallines^ there is a drawing 

 representing a number of disc-like ovaries attached to a tough 

 ligament, and referred to the mollusc Biiccinum, which bears a 

 certain resemblance to the Weymouth fossil. A similar body 

 is figured by Fuchs^ in an important memoir on supposed fossil 

 algae. 



It is not suggested that the Caulerpa Carruthersi of 

 Murray should be regarded as the cast of some molluscan 

 egg-case attached to a slender axis, but it is important to bear 

 in mind the possibility of matching such extremely doubtful 

 fossils with other organic bodies than the thallus of a Caulerpa. 

 In an example of an egg-case in the Cambridge Zoological 

 Museum, referred to a species of Pyrula, there is a hard, long 

 and slender axis, bearing a series of semicircular chambers divided 

 into radial compartments. The whole is hard and horny and 

 might well be preserved as a fossil. 



/9. Codiaceae. 



The members of this Order present a considerable diversity 

 of form as regards the shape of the plant-body ; the thallus of 

 some species is encrusted with carbonate of lime. The order 

 is widely distributed in tropical and temperate seas. 



Among the recent genera Penicillus and G odium may be 

 chosen as important types from the point of view of fossil 

 representatives. 



Godium. 



The thallus of Godium consists of a spongy mass of tubular 

 cell-branches which are differentiated into two fairly distinct 

 regions, an outer peripheral layer in which the branches have 

 1 EUis (1755) PI. xxxiii. a p. 80. » puchs (95) PI. viii. fig. 3. 



