182 DEVONIAN FAUNA. 



Unfortunately the material at our command has been too scanty to enable us 

 to get very clear sections, and it is only by a very careful examination that the 

 relations of the different parts of the structure can be made out as far as it has 

 been done. 



Affinities. — I find nothing at all like it in Ulrich's work. 



Fenestella conica, F. A. Romer, 1 seems to be just like its reverse face, but Romer 

 describes both sides of his fossil as similar. 



II. Family. — Acanthocladiidte, Zittel, 1880. 



This family is distinguished from the preceding by its mode of growth, being 

 formed of strong central stems and lateral branches, which may be free or may 

 combine with each other to form fenestrules, but have no non-poriferous 

 dissepiments, its form being thus dendroid, pinnate, or fenestrated. 



1. Genus. — Diplopora, Young and Young, 1876. 2 



" Zoaria consisting of very slender straight stems, which throw off a few 

 lateral branches of equal dimensions. Cells in two rows. Median keel moderately 

 developed." Ulrich 3 thus defines the genus, which he separates from Pinnato- 

 pora (Glauconome) as wanting pinnre. The species hitherto described are from 

 the Carboniferous Rocks. 



1. DlPLOPORA PRISTINA, 11. sp., PI. XX, fig. 4. 



Description. — Zoarium consisting of very slender, subcylindrical, slightly 

 curved branches, about *5 mm. in diameter, deeper than wide. Obverse side with 

 a double row of alternating apertures situated along the margins, to which thin 

 prominent peristomes give a slightly wavy outline. Apertures subcircular or oval, 

 opening obliquely outwards, with elevated peristomes, about "1 mm. in diameter, 

 twice their distance apart, and with five apertures to 2 mm. Keel elevated above 

 Hi'' apertures, bluntly angular, gently tuberculate. 



1 L850, I". A. Romer, 'Beitr. liar/...' pt. 1, p. 7, pi. i, figs. 13a, b. 



2 Schafhautl applied the name to an alga in 1863, but it does not seem, thei*efore, necessary to 

 change \ oung and Young's appellation, siDce the latest rules of nomenclature do not enforce changes 

 mii account of a word bein^ already used in the Vegetable Kingdom ('Bull. Soc. Zool. Fr.' for 

 L890, p. 38). 



:; 1890, (Jlrich, ' Geol. Surv. Illinois,' vol. viii, p. 398. 



