FENESTELLA. 173 



5. Fenestella sdbrectangularis, Sandberger. PL XIX, figs. 11, 11a, 12, 12 a. 



1855. Fenestella subbectangulabis, Sandberger. Verst. Rhein. Nassau, 



p. 376, pi. xxxvi, figw. 2— 3 ft. 



Description. — Zoarium very large, deeply convex and probably infnndibuliform, 

 constituted by small, narrow, straight branches, which are very convex on the 

 external or non-poriferous side, divaricate very rarely at ten or fifteen fenestrules, 

 and are united by very numerous broad, low, biconcave dissepiments. Fenes- 

 trules short-oval, becoming squarish when worn ; at the rate of eleven to 10 mm. 

 in length, and fifteen to 10 mm. in width. Cells in two ranges, alternating, and 

 at the rate to two cells in the length of a fenestrule. External surface smooth. 



Size. — Height of a large but imperfect frond 65 mm., width 70 mm. 



Locality. — There is one large (and perhaps one smaller) specimen from 

 Wolborough in Mr. Vicary's Collection ; a small specimen in the Torquay 

 Museum, a specimen from Lummaton in my Collection, and a specimen from 

 Lummaton in the British Museum. 



Remarks. — Mr. Vicary's largest specimen is the half of a deep cone, but it 

 cannot be said whether the cone in this and the other specimens was complete all 

 round. Mr. Vicary's second specimen has larger fenestrules, and the branches 

 divaricate much more frequently, besides which it appears to be flabellate rather 

 than conical, and therefore I am doubtful whether it belongs to the same species 

 as the rest. 



This species seems distinguished from the other Lummaton species by its long 

 straight, elevated branches, by its small number of cells, and by the short and 

 small fenestrules, which render it easily recognisable. Its external surface 

 approaches in general appearance the internal surface of Hemitrypa ocitlafa, 

 though differing in being decidedly coarser. 



An examination of Sandberger's beautiful figures makes me believe that in all 

 probability our present fossil belongs to his species. His figures accurately 

 represent our English specimens in every particular, except that in them the non- 

 poriferous side of the branches is striated instead of being, as in all the English 

 specimens I have observed, smooth. This, however, by itself, could hardly be 

 taken for more than a varietal difference, especially as it might possibly be due to 

 obliteration during fossilisation in our specimens, although they are certainly too 

 well preserved to make this likely. Sandberger, it is true, does not mention the 

 relative number of cells and fenestrules, but a comparison of his figures 2 a and 

 2 b give the impression that the former were twice as numerous as the latter. 



