BRYOZOA. 635 



ACANTHOCLADIA King, 1850. 



(Monograph Brit. Perm. Foss. p. 48.) 

 (For generic diagnosis see p. 398.) 



On plate LYI figures 1 to Ic, illustrate the internal charac- 

 ters of A. anceps Schlotheim, the type of the genus. According 

 to my observations, the zooecia are arranged about as follows: 

 In A. anceps there are generally four alternating rows of zooecia 

 on the main branch, but the number varies from three to six. 

 Of these the two central ranges are the principal ones, since 

 they run without interruption throughout the length of the 

 stem, while the one or two rows on each side of them are often 

 discontinuous. This fact argues a relationship to Septopora 

 that is better shown in A. fruticosa, in which, though with 

 ample room for them, the lateral rows are developed only along 

 the line of junction with the lateral branches. In both species 

 the lateral branches or pinnae have three ranges of cells. Another 

 feature common to both Septopora and A. fruticosa are the 

 small accessory pores. I have, however, not detected them on 

 the reverse side of the Permian species. 



ACAXTHOCLADIA FRUTICOSA UMch. 

 PI. LXV. fig. 2-2c. 



Zoarium strong, fruticose, pinnated, with the primary branch 

 giving off similar pinnated branches at frequent but irregular 

 intervals. Pinnae short, varying in length, between 1 and 3 

 mm.; 0.6 to 0.9 mm. wide, tapering slightly, with the free ends 

 obtuse. Primary branches' from 1 to 1.5 mm. wide, giving 

 off on each side, seven pinnae or lateral . branches in 1 cm. 



Obverse face showing three, often irregular alternating rows 

 of zooecia apertures on the pinnae, and two central rows on the 

 midribs. The latter are situated in two deep furrows, with six- 

 teen in 5 mm., and are generally flanked on one or both sides 

 by an intermediate row which more properly belongs to the 

 series that pass on into the pinnae and lateral branches. Aper- 

 tures circular, with no appreciable peristome, about 0.1 mm. 



