1 66 FREDERICK IV. SARDESON 



drawn out inosculations from which they may have arisen and 

 to side branches to which they are tending. The relation of 

 obverse and reverse of the frond is a little strange, since they are 

 reversed as compared to Phyllopori?ia, the basal expansion also 

 being unlike in that genus ; differences which I cannot explain, 

 but yet are of small import since closely related genera as Fen- 

 estella and Semicosmium differ in just that way. I feel not 

 assured that the primary basal expansion is known except in 

 Phyllopor/iia corticosa Ulr. 



DISCUSSION OF CRYPTOSTOMATA. 



These described species may suffice to represent the Cryp- 

 tostomata. The species of Pacliydictya and Rhinidictya are 

 of the Rhinidictyonidae ; Stictoporella and Ptilodictya of the 

 Ptilodictyonidae ; nothing especially different is seen in the Cys- 

 todictyonidae except sometimes a lunarium like that in the 

 Trepostomata; Rhombopora is of the Rhabdomesodontidae; Arthro- 

 clema of Arthrostvlidae ; Phylloporina of Phylloporinidae ; Sep- 

 topora of Acanthocladiidae ; and the Fenestellidae are merely 

 distinguished from the latter by having dissepiments without cell 

 apertures on them. In these all, and those which they are taken 

 to represent, the growth is acrogene and cell increase is almost 

 all axial. Axial and peripheral regions are sharply defined, cells 

 short, and mesopores filled more or less solid. 



The Cryptostomata differ in degree of specialization of 

 structures rather than in kind from the Trepostomata. In fact, 

 they are arbitrarily divided in all respects. The defined axial 

 and peripheral regions of zoarium appearing to arise in Treposto- 

 mata are merely as strongly to stronger developed in Crypto- 

 stomata. So also are the long, tabulated cells changing to 

 shorter, with or without tabulae and so-called hemiphrams or 

 hemisepta. Peripheral cell increase is only reduced to nearer 

 the minimum. The mesopores begun apparently as young cells 

 in Trepostomata and developing to subordinate special struc- 

 tures or vesiculose to solid interstitial filling, are vesiculose to 

 solid in Cryptostomata. Monticules ranging to the extreme 



