PALE0NTOLOGIC CONTRIBUTIONS 



19 



jjtfifc 



aspects of the apertural processes. Frequently the two prongs are 

 pressed one upon the other and many of the processes appear there- 

 fore simply club-shaped; others, however, show distinctly the fork, 

 and in others again the fork, in being 

 torn from the branch to which it was 

 attached, seems either to have taken with 

 it a piece of periderm and thus appears 

 peltate (see text fig. 7) or it had actu- 

 ally broadened into an irregular attach- 

 ment disk. This seems of interest inas- 

 much as Wiman has described a species 

 of Dictyonema with exactly such ter- 

 minal prongs, as D . cervicorne, 

 and another with irregular patches at the 

 ends of the filamentous apertural process 

 as D. p e 1 1 a t u m . It is possible that 

 our earlier species leads to this whole 

 group of aberrant types, represented by 

 D. cervicorne, peltatum, 

 tuberosum and cavernosum. 

 Halm in his genealogic chart of the 

 Dendroidea, considers his C a 1 1 o - 

 g r a p t u s g r a b a u i (—Dict- 

 yonema furciferum) as leading ™ ann )- 7 Fragmentary rhab- 

 f rom D . f 1 a b e 1 1 i f o ■ r m e var. 

 ruedemanni to Dendrograp- 

 tus fluitans. From present evi- 

 dence it appears that it rather leads from D. flabelliforme 

 to the aberrant group mentioned above, which in Hahn's chart is 

 given an isolated position. 



Hahn referred his species to Callograptus, comparing it with 

 C . s a 1 1 e r i and C. compactus. The reason for this refer- 

 ence appears from his statement that " very seldom one or the other 

 of these apertural processes reaches the neighboring branch, join- 

 ing it like a dissepiment. While well-preserved material shows 

 that as a fact all apertural processes reach the neighboring branch, 

 whereby a network identical in aspect with that of Dictyonema 

 arises, Hahn is nevertheless right in seeing in this form not a typical 

 Dictyonema, for there the branches are regularly connected by true 

 dissepiments instead of apertural processes. In Callograptus, by 

 Hall's definition, the branches are sometimes distantly and irregu- 

 larly united by transverse dissepiments. The species here discussed 



Fig. 7, 8 Airograp- 

 tus furciferus (Ruede- 



dosome with apertural pro- 

 cesses (x 4). 8 Fragment of 

 another specimen, (x 4) 



