B 



THALLOPHYTES, BRYINAE. 41 



those of the second order, it may further be concluded that the latter, 

 like those of Naomeris, were as a rule only two in number and occupied 

 the median position, for two pores in the peripheral calcareous layer 

 answer to a ring of pores on the axile tube. But this is not observed with 

 perfect regularity in all cases. More searching investigation will probably 

 show the existence of a variety of specific differences. 



Among forms of more complicated structure are some which, like 

 Zittelina, Mun. Chalm. and Terquemella, Mun. Chalm., are undoubtedly 

 allied to the recent genus Bornetella, Mun. Chalm. But since the remark- 

 able structure of Bornetella has nowhere been as yet fully described, and a 

 monograph of the entire group cannot be introduced into this place, a 

 minute description of the fossil genera is at the present moment scarcely 

 possible. There are also genera in which the construction is still quite un- 

 explained ; one of these 

 is a form of very fre- 

 quent occurrence, Thyr- 

 soporellacribrosa 1 , Giim- 

 bel (Dactylopora, Mun. 

 Chalm.), which I have 

 had the opportunity of 

 examining in many speci- 

 mens. 



Some genera are of 

 more simple structure, 

 but it is not yet quite 

 certain that they belong 

 to the class of which we 

 are speaking. They are 



frmnrl in thf> Triac anrl FIG. 4. A transverse section of a piece of stone from the Keuper of the 



db, ctllU A , ps of g outhern Tyrol pierced with Diploporae. B interior of a 



rvrrnr P:nprip11v in thf Diplopora from Esino. C surface-view of Gyroporella vesiculifera from 



u-v_ui cojJtuicmy in Liic Inzino in Lombardy. D longitudinal fracture of the same from San 



Q/~ii+-1-><rn A IT-.O tirV>/*-,a Michele on the lake of Garda ; the cast which fills the axile tube is pre- 



OOUUieri .tt.ipb, Wliere served in the lower part of the figure. E surface of detached cast of the 



they form rocky masses ffi&f the same species ' A twice 

 of very great thickness 2 . 



Their mode of preservation is different from the above, since all their cavities 

 are usually filled with the material of the rock in which they lie ; and if a 

 canal still remains open in the wide tube of the main axis, its walls are 

 usually lined with crystals closely crowded together. Diplopora annulata, 

 Giimbel 3 , and its allies (Fig. 4 A, B}, which are peculiar to the Muschelkalk 

 of the Alps and to the Lower Keuper (Mendola dolomite, Wettersteinkalk), 

 have a long cylindrical obscurely segmented thallus with a dome-shaped 



C 



1 Giimbel (1), t. D I, f. 13. 



8 Benecke (1). 



Giimbel (1). 



