Genera of the ISTorth American Palaeozoic Bryozoa. 559 



larger, as in Lichenalia cultellata, where the diameter is from 

 two to four times that of an autopore; and it seems almost a 

 rule that the smaller the autopores, the larger the vesicles pro- 

 portionally. 



The forms of Fistulipoea so gradually pass into other genera of 

 undoubted Bryozoa, that sometimes it is difficult to distiaguish 

 the genera apart, especially from fragments. Fistulipora eellata 

 and Introjpora jputeolata have the cells and intercellular tissue so 

 similar, that it is only possible to distinguish the two genera by 

 their mode of growth ; the one consisting of lamellate incrusta- 

 tions, and the other of bifoliate, dichotomously divided, flattened 

 branches, with noncelluUferous margins. 



Fistulipoea, McCoy. 



(Ann. and Mag. Nat. Hist, 2d Series, Yol. Ill, p. 130. 1849.) 



Type, Fistulipora incrnstans, Phillips (sp.). 

 (Plate 22, figs. 11-13.) 



Zoarium incrusting or massive, under surface of explanate 

 forms consisting of a wrinkled epitheca ; cells tubular, tabulate ; 

 with two more or less prominent pseudosepta along one side, 

 giving a bilobed or trilobate form to a section of the cell ; inter- 

 cellular space, near the base, occupied by irregularly disposed 

 vesicles; above by vesicles or tabulated mesopores; sometimes 

 the vesicles are so regularly superimposed that they resemble the 

 tabulate mesopores; cell apertures irregularly and generally 

 closely disposed, bilobate or trilobate in outline, and having on 

 the septate side a prominent lunarium; interapertural space 

 occupied by mesopore apertures or vesicular cavities ; surface 

 usually with monticules or maculae, the centers of which are 

 generally occupied only by angular pits, the cell apertures imme- 

 diately surrounding them being larger than those on other por- 

 tions of the frond. 



Lichenalia, Hall. 



(Pal. IST. Y., Yol. II, p. 171. 1852.) 



Syn., Dylowskiella. Type, Lichenalia concentrica^ Hall. 



(Plate 23, figs. 8-10; PI. 23, figs, 1-6.) 



Zoarium having the same general appearance and manner of 



growth as Fistulipora., but the interapertural surface is solid. 



