OE CRETACEOUS PLANTS. 243 



Genus DIPLOPORA, Sohafhiiutl. 

 [Siid-Bayerns LetliEea Googn. Petrefacten, 1863, pp. 324, 327.] 



The generic name was first given to forms which. Schafhautl 

 included among the Brj'ozoa. Later by Giimbel and others 

 it was superseded by Gyroporella, but the older name was 

 revived for some of the algal forms which are characteristic of 

 the Trias ; and the name is also used by Lorenz and Arbenz for 

 the Cretaceous species which they describe as follows : — 



Diplopora Milhlbergii, T. Lorenz. 



1902. Diplopora Miihlbergii, T. Lorenz, Bericht Naturf. Ges. Zurich, 



vol. 12, pp. 19 [52]-20[53], figs. 3-7. 

 1908. Diplopora Muhlheryii, Lorenz, Arbenz, Vierteljahrsschrift 



Naturf. Ges. Zurich, vol. 53, pp. 387-392, figs. 1-5. 



Slender, somewhat bent tube-like forms, average length about 

 2 mm. (?) From the hollow axial space open whorls of branch 

 canals. The branches vary, but are principally simple. Branch 

 whorls are separated some distance from each other and the 

 branches are not superimposed in vertical series. In a variety 

 described by Arbenz (1908) the average diameter is 0'3-0'5 mm., 

 with a thickness of 0'1-0'15 mm. for the wall. 



HoKizoN, — Barremian and Aptian. 



LocALiir. — Wildkirchli and elsewhere, locally very abundant. 



Lorenz notes that the discovery of this form in the Cretaceous 

 is of interest, because hitherto algse of this generic type have 

 been known in numbers only from the Trias, with isolated 

 specimens from the Jura. According to Arbenz (1908) the 

 alga is extremely abundant in the Lower " Sohrattenkalk " 

 (Up. Barremian) and Aptian of some districts, and may even 

 form one third of all the organisms in a deposir.. He says 

 (p. 392) " Die Diploporen der untern Kreide scheinen somit 

 auf das Barremien und Aptien iu neritischer Faoies beschrankt 

 zu sein," where they are a typical facies fossil. 



The name 2). Milhlbergii probably covers several species 

 which can only be separated when more detailed work is 

 available. 



k2 



