AIGJE. 6 



remains, originally mentioned as species of the genus Algaoites, are 

 referred to various recent genera to which some resemblance in 

 external form is considered to exist. The name Algacites has since 

 been replaced by other terms, and appears to be no longer used 

 as a general designation of fossil Alga of doubtful affinity. There 

 is another term, Fucoides, which has also been used by Sternberg 

 and many other palseobotanists in an equally wide sense, but such 

 a name naturally suggests a certain resemblance to the recent 

 genus JFucus, and is thus unsuitable if used in a more com- 

 prehensive sense. 



This suggestion as to the use of a provisional and wide generic 

 designation, such as Algites, may be considered a retrogressive 

 step and likely to lessen our accurate knowledge of fossil Alga. 

 If the data were generally adequate, and afforded sufficient 

 indication of botanic affinity, any such term would be superfluous. 

 When we consider how exceptional it is to find ourselves in a 

 position to make definite statements, founded on satisfactory 

 evidence, as to the family of Alga in which fossil forms should be 

 placed, it must he admitted that we are lessening the possibilities 

 of error by the return to more general and less definite terms. 



Botanists would naturally prefer to pass over such markings 

 or casts which are too imperfect to admit of identification ; but in 

 spite of their apparent worthlessness from a botanical point of view, 

 they may be of service to the geologist, and indeed the most 

 fragmentary material may become important when more perfect 

 specimens have been discovered. Thus it is better to place on 

 record even those exceedingly doubtful fossils, and to adopt a 

 provisional name in the hope that future discoveries may throw 

 more light upon family or generic affinity. Generic names, such 

 as Sphenopteris, Pecopteris, etc., of Brongniart have served a most 

 useful purpose, and by degrees these are being replaced by more 

 definite botanical titles as fertile specimens are discovered, and so 

 afford clues as to natural affinity. As another instance of a 

 convenient term we may mention Rachiopteris, which Williamson 

 has applied to those fragments of fern petioles which it is not 

 possible to refer to particular genera. 



