100 



of a fenestrule, separated by obscure and delicate undulating striae. Reverse apparent!^ 

 smooth. 



I have little doubt as to the identity of our specimens with those described by Prout, 

 though there are some trivial differences. From P. pulcliella, (Nich.) the present species is 

 readily distinguished by the more robust branches, the greater length of the fenestrules and 

 their smaller width, as well as by the possession of four, instead of three, rows of cells. 



Locality and Formation. Rare in the Corniferous Limestone of Lot 6, Con. 1, Wain- 

 fleet, 



122. POLYPORA TENELLA (Nicholson). 



Polypora tenella (Nicholson), Geological Magazine, April, 1874. 



Polyzoary small, forming a flattened expansion ; branches radiating from the base, and 

 increasing by bifurcation at intervals of about two lines. Branches narrow, about eight in the 

 space of a quarter of an inch, their width being about a quarter of a line. Fenestrules oval, 

 about eight or nine in a quarter of an inch, measured longitudinally, and ten in the same space 

 measured transversely ; the length of each about half a line, the width a third less. Dissepi- 

 ments very short and narrow, without pores. Cells arranged in three alternating rows on the 

 branches, opening by minute rounded apertures, two or three of which occupy the space of a 

 fenestrule. Reverse unknown. 



This pretty little species is distinguished from 

 the preceding forms by its much more delicate pro- 

 portions, its narrower and more closely set branches, 

 and its much smaller fenestrules. 



Locality and Formation. Rare in the Cornife- 

 rous Limestone of Lot 6, Con. 1, Wainfleet. 



Fig. 36. 



rt. Fragment of the cast of Polypora Halliana, 

 (Prout), magnified ; 6. fragment of the cast of Poly- 

 pora tenella (Nich.), enlarged. From the Corni- 

 ferous Limestone. 



123. POLYPORA TUBERCULATA (Nicholson). 



Polypora tuberculata (Nicholson), Geological Magazine, April, 1874. 



Polyzoary small, forming a flattened expansion which springs from a strong foot-stalk. 

 Branches radiating from the base, and increasing by bifurcation at intervals of about a line 

 and a half, from a third to half a line in breadth, rounded, and destitute of carinae. Dissepi- 

 ments very short, widest at their junction with the branches. Fenestrules somewhat irregu- 

 lar in shape, usually a very long oval, always longer by from one half to two-thirds than wide ; 

 having an average width of a third of a line to half a line by a length of one line or a little 

 less. Two fenestrules in two lines measured longitudinally, and four in the same space meas- 

 ured transversely, those of contiguous rows being usually opposite or nearly opposite. Disse- 

 piments non-poriferous. Four (sometimes three) alternating rows of cells on each branch, opening 

 by minute rounded pores, which are prominently elevated above the general surface. Five pores 

 to the length of a fenestrule. Reverse unknown. 



Polypora- tuberculata differs from all other 

 recorded species of the genus, except P. verm. - 

 cosa (McCoy), by the possession of prominent- 

 edged pores, which give to the celluljferous sur- 

 face of the branches a peculiar tuberculated 

 appearance. The latter, however, has exceed- 

 ingly long and narrow fenestrules, with nearly 

 twice as many pores to the length of a fenes- 

 Fig. 37. trule. I have only seen fragmentary examples 



a. Fragment of Polypora tuberculata (Nich.), natural size ; of flip 

 6. The same enlarged ; c. Portion of a branch, still further 

 enlarged. ^[Frorn the Hamilton group. 



