158 THALLOPHYTA. [CH. 



coniferous twigs, the tracks and burrows of various animals and 

 other objects have been described by several authors as fossil 

 species of Gaulerpa. As an illustration of the identification of a 

 very doubtful fossil as a species of Caulerpites, reference may be 

 made to such a form as G. cactoides Gopp.' from Silurian and 

 Cambrian rocks. There are several examples of this fossil 

 in the Brussels Museum which probably owe their origin to 

 some burrowing animal, and may be compared with Zeiller's 

 figures of the tunnels made by the mole-cricket (fig. 30, 4)''. 



Mr Murray, of the British Museum, has recently described 

 what he regards as a trustworthy example of a fossil Gaulerpa 

 from the Kimeridge Clay near Weymouth'. Specimens of the 

 fossil were first figured in a book on the geology of the Dorset 

 coast as casts of an equisetaceous plant*. 



To this fossil Murray has assigned the name Gaulerpa 

 Garruthersi, and given to it a scientific diagnosis. The best 

 specimens have the form of a slender central axis, giving off 

 at fairly regular intervals whorls of short and somewhat clavate 

 branches; they bear a superficial resemblance to such a 

 recent species as Gaulerpa cactoides Ag. An examination of 

 several examples of this fossil leads me to express the opinion 

 that there is not sufficient reason for assigning to them the 

 name of a recent genus of algae ^ To use the generic name of 

 a recent plant without following the common custom of adding 

 on the termination " ites " (i.e. Gaulerpites) is as a general rule 

 to be avoided in dealing with, fossil forms; and there are, 

 I believe, no satisfactory grounds for referring to these fossils 

 as trustworthy examples of a Mesozoic alga. 



In the present case I am disposed to regard the Gaulerpa- 

 like casts as of animal rather than plant origin. The clavate 

 branches have the form of very deep moulds in the hard brown 

 rock which have been filled in with blue mud. It is hardly 

 conceivable that the branches of a soft watery plant such as 

 Gaulerpa could leave more than a faint impression on an old sea- 

 floor. The specimens occur in different positions in the matrix 



1 Goppert (60) p. 439. PI. xxxiv. fig. 8. 



2 Zeiller (84). 3 Murray G. (92) p. 11; also (95) p. 127. 

 " Damon (88) PI. xix. fig. 12. » Vide also Eothpletz (96) p. 894. 



