FENESTELLA. 165 



part of cell oblong, quadrate, or hexagonal in outline. Superior hemiseptum usually- 

 present. Primitive aperture semi-elliptic. Superficial aperture rounded with peri- 

 stome (and in the perfect state closed by a centrally perforated operculum). 



1. Genus. — Fenestella, Lonsdale, 1839. 



" Zoarium flabellate to infundibuliform, poriferous on the inside (always?), 

 branches nearly straight, and united at rhythmical intervals by non-poriferous 

 dissepiments. Zooecia in two rows, separated by a more or less developed median 

 keel." 1 Silurian to Trias. 



Originally defined by Lonsdale, 2 this genus was afterwards considerably 

 extended by him, 3 and then again restricted by King, 4 whose definition does not 

 differ materially from that adopted by Ulrich, and given above. It may, however, 

 be noticed that Phillips distinguishes the genus from Betepora by its having the 

 poriferous side external ; but Lonsdale and King describe this as sometimes internal 

 and sometimes external, while Ulrich describes it as " on the inside (always ?)." 



It appears from Scudder 5 that the name Fenestella was used in 1819 by Bolton 

 (' Mus. Ed.,' ii, p. 134) for some bivalve. I have been unable to trace this reference 

 further, but expect that it probably is a mere unautboitative catalogue name, as 

 it has never been recognised as valid for a mollusc. 



1. Fenestella fanata, 6 n. sp. PI. XVIII, figs. 6 — 10, and PI. XIX, figs. 3, 4. 



1840. Fenestella antiqua, Lonsdale (not Ooldfuss), pars. Geol. Trans., ser. 2, 



vol. v, pt. 3, pi. lviii, figs. 10 — 10 i. 

 18-11. — — Phillips, pars. Pal. Foss., p. 24, pi. xii, fig. 35/3, y 



(only). 

 1849. — — d'Orbigny. Prodrome, vol. i, p. 101. 



Description. — Zoarium widely cup-shaped, growing from a wide base. Fenes- 

 trules 8 or 9 in the length of 10 mm., and 16 in the width of 10 mm. ; elongate, 

 oval or oblong, rather variable in size and shape in different parts of the 

 same frond. Branches narrow, not very straight, subcircular in section, about 

 the same width as the fenestrules, though sometimes wider or narrower, swelling 



1 1890, Ulrich, ' Geol. Surv. Illinois,' vol. viii, p. 395. 



2 1839, Lonsdale, in 'Mureh. Sil. Syst.,' vol. ii, p. 077. 



3 1845, Lonsdale, in Murchison, Keyserling, and Verneuil, ' Russia,' Appendix a, p. 629. 



4 1851, King, ' Permian Fossils,' p. 34. 



5 1882, Scudder, ' Nomenclator Geol.,' p. 138. 



6 Lummaton being in the parish of St. Mary Church. 



