FOSSIL ALG^E. 41 



plant. It must have formed a noble sea-weed with stems 

 several feet in circumference recalling in stature the Fuca- 

 ceous and Laminarian giants of our southern seas, and 

 in girth at all events surpassing them. There is no evi- 

 dence of calcification here, and the presence of tenacula 

 would secure the cohesion of the tubes which are not so 

 much interwoven as those of Avrainvillea, for example, 

 which dispenses with both calcification and tenacula. Since 

 Udotea, however, which it most resembles, possesses en- 

 crustation nearly always slight but varying in amount in 

 different species, in addition to tenacula, it is possible that 

 we may owe the preservation of Nematopkycus to a slight 

 calcification though no trace of it remain. Disregarding 

 Pachytheca as a doubtful case we must leave the primary 

 rocks with this sole veritable representative of the Algae. 



It is difficult to say definitely what is to be made of 

 Bertrand and Renault's Pila bibractensis (6) of the Permian 

 epoch. Its authors describe it as a gelatinous Alga with an 

 ellipsoid, multicellular thallus, and appear to see farther into 

 its nature than one is quite prepared to accompany them. 

 It is impossible to assign it a place, and there is in point 

 of fact little to be said and more to be doubted with regard 

 to this remarkable production. 



In the great sweeping away of spurious fossil Algae the 

 Secondary rocks were left quite destitute of any true claim- 

 ant to recognition until we come to the top of the series 

 in the Cretaceous beds which contain diatoms and Litho- 

 thamnian (Senonian beds). The forms of Bactryllium of 

 Triassic age may eventually be found to survive this denial 

 of their claims as Algae, and the possibly Siphonaceous 

 Diplopora from the Muschelkalk and Lower Keuper, 

 Munieria and Triploporella from Cretaceous beds, are even 

 more likely to receive adoption into the series of true Algae. 

 The present writer described (9) a fossil Caulerpa (Sipho- 

 ned) from the Oolite (Kimmeridge Clay) of which very com- 

 plete casts in the round are preserved, and it is noteworthy 

 as the remains of an Alga which was not encrusted with 

 any mineral secretion. In these last days Mr. Seward 

 (10), in his admirable account of the Wealden flora given in 



