Reviews — Dr. D. Stur — Fossil Ferns of the Coal-measures. 331 



Daneites, Goppert. — There is additional information given on this 

 genus, which, approaches closely in some points to the genus Dancea. 



In " PoLYPODiACE^ ? ? ?," evidently with considerable doubt, Stur 

 includes the following genera : — Thyrsopteris, Kze. ; [Falceofhyr- 

 sopteris) ; Calymmotheca ; Sorotheca ; and Diplothmema. 



Thyrsopteris, Kze. — It would be much better to adopt the name 

 Palceotliyrsopteris for this genus, as Stur has proposed, in the event 

 of the fossil proving to be different from Thyrsopteris. Their identity 

 has not yet been determined, so the use of the genus Thyrsopteris for 

 his fern {T. schistoriim, Stur) appears scarcely admissible. 



Calymmotheca, Stur. — We are inclined to think that Dr. Stur has 

 included in this genus, two distinct forms of fructification. Those 

 originally described in the Culm Flora as Calymmotheca form one 

 type, the other type is represented by Caly. Avoldensis, Stur, and 

 Caly. Frenzli, Stur, which are described in the present work. 



In the fructifications originally placed in Calymmotheca, we have 

 a number of exannulate sporangia springing from a common point of 

 attachment. This we believe to be the true explanation of the 

 structure of this fruit, and was first pointed out by Eenault,' but 

 more fully elucidated by Zeiller.^ Dr. Stur, hewever, still regards 

 these sporangia as so many ribbon-like shreds of a split involucre or 

 capsule, a view we regard as quite untenable, both from the evidence 

 adduced by previous writers and the examination of beautifully pre- 

 served specimens which have come under our notice. 



In Caly. Avoldensis and Caly, Frenzli, we have, however, a very 

 different structure. Here we evidently have an involucre and in 

 some specimens of another species, with the same type of fructifica- 

 tion, we have been able to trace the involucres through all their 

 stages of development, — they are at first globular, but at maturity 

 split into four valves for the dissemination of the spores. There is 

 a further difference between these two types of fruit. In Calym- 

 motheca (as originally employed by Stur) the fruiting portions of the 

 fronds are entirely deprived of foliage pinnules, whereas in the other 

 type ( Caly. Avoldensis and Caly. Frenzli) a very slight modification 

 takes place in the fruiting fronds, which are not deprived of the 

 ordinary foliage pinnules. These two forms are apparently generic- 

 ally distinct. The Calymmotheca proper probably belong to the 

 MarattiacecB, while the other type is perhaps related to the Hymeno- 

 phyllacecs. 



Sorotheca, Stur. — This genus is evidently similar to Crossotheca, 

 Zeiller.^ The specimens studied by Zeiller appear to have been more 

 complete and in a better state of preservation than those examined 

 by Stur. As the sporangia are exannulate, it is impossible to place 

 this genus in the Folypodiacece. 



Diplothmema, Stur. — This genus as at present constituted does not 

 appear of much practical use, as it contains many species which have 

 evidently little affinity with each other. Some time ago, Zeiller 

 proposed for Sphen. latifolia, Brongt. ; Sphen. acuta, Brongt. ; Pec. 



1 I.e. p. 182, pi. ix. fig. 10, 11. 



^ Cours d. botaii. foss. Troisieme Annee. p. 198, 1883. 



3 I.e. p. 180, pi. ix. figs. 1-11. 



