COASTS VISITED BY THE AECTIC EXPEDITION. 621 



Genus Polypoka, M'Coy, 1844. 

 (Synop. Carb. Eoss. Ireland, 1844, p. 206.) 



Polypoka gkakdis, Toula? 



Polypora grandis, Toula, IS". Jahrbuch, 1875, p. 230, t. 9. f. 7. 



Sp. char. Interstices flat, broad, and increasing in size previous 

 to bifurcation ; dissepiments thin, usually oblique and striated ; 

 fenestrules large, elongate obliquely and rhomboidal, narrow, occa- 

 sionally irregular ; apertures of the cells arranged on the interstices 

 in oblique rows, five or six to the row. 



Obs. The broad flat interstices and narrow, much elongated 

 fenestrules will, I think, be sufficient to separate the two specimens 

 I have recorded under this name and those I have placed under P. 

 fastuosa, De Koninck. Whether they are P. grandis, Toula, how- 

 ever, is a point open to discussion. The specimens in question agree 

 with Dr. Toula's description and figures in the broad, flat, conspicuous 

 interstices and narrow elongated fenestrules ; but, on the other hand, 

 the dissepiments are not so regularly oblique in our form, but are, 

 for the most part, horizontal. As I am averse to creating a new 

 species when a reference to a known one can possibly be made, even 

 by a slight extension of its characters, I provisionally place these 

 specimens under Dr. Toula's species. 



Polypora grandis, in the size of its interstices and fenestrules, is 

 allied to P. {Betepora) laxa, Phill.*, and again, irrespective of the 

 generic differences, to Fenestella coassa, M'Coy. In P.? laxa, 

 however, the network of the polyzoarium is much more irregular 

 than in P. grandis, although this is less marked in Phillips's second 

 and later figure of his species f . 



Loc. Peilden Isthmus, lat. 82° 43'. 



Polypoka megastoma (De Koninck?). 



Fenestella megastoma, De Kon. Quart. Journ. Geol. Soc. 1863, 

 xix. p. 5, t. 2. f. 3. 



Sp. char. Polyzoarium expanding, inclined to be irregular; inter- 

 stices subparallel, slightly thicker than the dissepiments, bifurcating 

 at intervals, with very little apparent thickening at each bifurca- 

 tion ; dissepiments horizontal, subalternate in contiguous rows, here 

 and there nearly opposite ; fenestrules parallelogrammic, with rounded 

 angles, longer than wide, sides not indented or overhung by the cell- 

 apertures ; cell- apertures numerous, arranged regularly in quincunx 

 and confined to the interstices ; reverse striate. 



Obs. I cannot find any more fitting reference for the form repre- 

 sented than Prof, de Koninck's Indian species. One of the spe- 

 cimens I so refer is of about the same dimensions as, the other 

 somewhat smaller than the Indian form ; but in both there are to be 

 observed the essential characters assigned by Prof, de Koninck to 

 Lis species — the interstices and dissepiments of equal dimensions, 



* Geol. Yorksb. 1836, ii. p. 199, 1. 1. f. 26-30. 

 t Pal. Foss. Devon, 1841, p. 23, t. 12. f. 34. 



