BRYOZOA. 639 



PHYLLOPORINA Ulrich. 



(For generic diagnosis see page 399.) 



After extended study this genus was established for the recep- 

 tion of a well marked group of Silurian Bryozoa. Nicholson's 

 Retppora trentonensis, and Hall's R. asperatostriata are regard- 

 ed as the typical species. The earliest species known belong to 

 the Chazy group from which horizon I figured .one (PI. LIII, 

 fig. 4,) that is identified with Hall's Gorgonia? aspera. It is a 

 peculiar form and differs widely from the ordinary species of 

 Phylloporina, among which it is now placed with some doubt. 

 The other species that should be removed to the new genus are 

 Retepoia trentouensis Nich., Intricaria ivticulata Hall, Phyllo- 

 pora corticosa Ulr. (Trenton): Intricaria clatbrata M. & D., 

 Phrllopora variolata Ulr. (Gin. gr.); Retepora angulata Hall, 

 (Clinton); and R. asperatostriata Hall. (Niagara). Several new 

 species are known, one of them (P. dawsoni) is briefly defined 

 on page 331 and the internal structure very well illustrated on 

 PL LIII. 



PHYLLOPORINA GRANISTRIATA Ulrich. 



PL XXIX, Fig. 3-3a. 



Zoarium an undulated expansion, consisting of more than 

 ordinarily rigid, slender branches, from 0.3 to 0.5 mm. in width, 

 that inosculate at rather long but irregular intervals. Fene- 

 strules narrow, with an average length of about four mm., but 

 varying from two to six mm.; width from 0.2 to 0.7 mm. Re- 

 verse with fine, granulose, longitudinal striae. Celluliferous side 

 not seen. Zooecia (as observed in sections) tubular, arranged 

 in three rows. Apertures circular, with a small peristome, 0.09 

 mm. in diameter, ten or eleven in two mm. Rows of cells sepa- 

 rated by slightly elevated carinae, bearing one small acantho- 

 pore to each zooecium. 



This species is allied to P. reticulata Hall, and P. dawsoiii. 

 From the first it is distinguished by the stronger branches and 

 much larger fenestrules. From the second by the same differ- 



