184 DEVONIAN FAUNA. 



branches approximately parallel, and united with each other by numerous short 

 lateral branchlets, which sometimes seem free, sometimes meet at an angle, and 

 sometimes are so short and straight as to have the character of simple dissepiments, 

 nearly equal to the secondary branches in size and forming elongate irregular 

 fenestrules between 1 and 2 mm. in length, from the summits of which new 

 branches occasionally arise ; the network becoming more lax and disconnected 

 near the margins. Intimate structure unknown. 



Size. — A defective specimen is 30 mm. long, and 20 mm. wide. 



Locality. — A single specimen is in the Torquay Museum. Its locality is 

 unknown, but its matrix is very similar to the limestones of Lummaton or 

 Wolborough. 



Remarks. — The face of this fossil being worn, it is impossible to discover any 

 structural characters, but from its close resemblance to some American forms 

 there seems no reason to doubt that it belongs to the genus Septopora. The 

 fenestrules appear to be really formed by amalgamated branchlets, and sometimes, 

 especially near the margins, these become very irregular, though occasionally 

 the lateral bars are so short and straight (as in the figured portion) that there is 

 nothing to distinguish them from dissepiments. 



It could not be assigned to the genus Ptilopora, because its primary branches 

 are numerous and its fenestration much less regular. 



Affinities. — From Septopora biserialis, Swallow, var. nervata, Ulrich, 1 it differs 

 in having the secondary branches set at a greater angle, and in having larger 

 and more elongate fenestrules. From S. pinnata, Ulrich, 2 it differs in its more 

 complete, regular, and elongate fenestration, and in the diminishing character of 

 its secondary branches, but it certainly nearly approximates to the latter species. 



3. Genus. — Ptilopora, M'Coy, 1844. 



Zoarium pinnate, the median branch stronger than the oblique lateral 

 branches. Lateral branches united by frequent non-poriferous dissepiments. 

 Zooecia in two rows. 



1. Ptilopora (?), sp. PI. XX, fig. 6. 



Descrijitioii. — Zoarium pinnate, with a long cylindrical central stem. Side 

 branches small, set at a very wide angle to the central stem, and united by very 

 broad dissepiments, which thus appear to form short oval irregular fenestrules. 



1 1890, Ulrich, ' Geol. Surv. Illinois,' vol. viii, p. G32, pi. G4, fig. 6. 



2 Ibid., vol. viii, p. 033, pi. lxiv, fig. 7 ; and pi. lxv, tigs. 1, la. 



