36 THALLOPHYTES, BRYINAE. 



which, at the present time at least, live only in the sea, and are entirely 

 wanting in the other beds. It is very remarkable that absolutely no plants 

 of this group have been discovered in the formations below the Senonian. 

 It is true that Castracane l obtained from the ash of English coal at Rome 

 eight species of common fresh-water Diatoms ; but the statement has never 

 been confirmed, and though the author assures us that he adopted every 

 measure of precaution, it must be regarded with the greatest suspicion, 

 especially since Williamson 2 has failed to find any such forms after ex- 

 amining coal from twenty-two different seams in order to determine the 

 point. Pfitzer in the article just cited has expressed the opinion that the 

 group made its appearance for the first time in the Upper Chalk. This 

 appears to me on many grounds highly improbable. It is important 

 to consider whether renewed investigations would not result in further in- 

 teresting discoveries, for no one since Ehrenberg seems to have taken the 

 subject seriously in hand. 



The only organic remains from the older formations, which have been 

 supposed to belong to Diatomaceae, are the forms of the genus Bactryllium 

 which have been studied chiefly by Heer 3 . These are small red-shaped bodies 

 of very peculiar and doubtful character, rounded or almost rectangularly cut 

 off at both extremities and pressed quite flat, each having a single furrow 

 on the broader side, or two furrows separated by an intervening cushion. 

 Their rather thick wall incloses, according to Heer, a cavity which is filled 

 with the stony mass. In some forms a transverse striation is seen on the 

 broader surface on both sides of the central furrow. The largest species, 

 such as B. Schmidii, Heer, are as much as four millimetres in length. The 

 comparison with Diatomaceae rests entirely on the external appearance ; the 

 furrow in the middle was supposed to correspond to the division between 

 the valves, and the transverse striation to be analogous with the sculpturings 

 upon them. The vegetable nature of these organisms is not certainly ascer- 

 tained, and further examination of them is desirable. Bactryllia are found 

 in the Keuper of the Alps and of the North of Switzerland, and are par- 

 ticularly plentiful in the Sankt Cassian beds, where they lie massed 

 together in the slates. According to Schimper 4 they also occur in the 

 Muschelkalk near Heidelberg. 



We are acquainted with fossil remains from several groups of the series 

 of Chlorosporeae. The Characeae are represented in the Quaternary and 

 Tertiary formations by a considerable number of species, which, as far as 

 we are able to determine, agree entirely with recent forms. A number of 

 species are known also from older formations, Chara Jaccardi, for example, 

 from the Lower Chalk of the Canton of Neufchatel and Ch. Bleicheri from 



1 Castracane '!). 2 Williamson '1 , x, p. 519. 3 Heer (2; and (3). Zitlel (1). 



