GENERA OF FAVOSITID^E. 129 



concentrically-wrinkled epitheca. Average size of the corallum 

 from an inch or less up to three inches in diameter, with a 

 height of from five to fourteen lines. Corallites extremely 

 oblique, compressed, from one-third to one-half of a line in 

 their long diameter, and less than this in their short diameter. 

 Calices upon the upper surface very oblique, subtriangular, or 

 somewhat lozenge-shaped, usually bounded by one long and two 

 short curved margins ; upon the lower surface, where present, 

 usually less oblique, and often irregularly polygonal. Septa 

 numerous, in the form of pointed spines, which have a marked 

 upward direction, and extend into the visceral chamber to about 

 one-third of its diameter. Tabulse numerous, complete, hori- 

 zontal. Mural pores apparently comparatively numerous and 

 of no large size. 



Obs. This is one of the most abundant of the corals of the 

 Wenlock Limestone of Britain. If the Devonian A. suborbicu- 

 laris, Lam., be considered, as has here been done, to include only 

 forms which grow into irregular masses composed of superposed 

 concentric strata of corallites, then the present species is easily 

 distinguished from it by the difference of its ordinary habit. It 

 forms flattened expansions, attached by a pedunculate base, and 

 usually having part of the lower (as well as the upper) surface 

 covered by calices. Sometimes almost the whole lower surface 

 is so occupied, but generally a portion seems to have been pro- 

 tected by an epitheca. In general form, therefore, A. Labechei, 

 E. and H., resembles the A. Goldfttssi, Bill., of the Devonian 

 of North America; but the latter is readily distinguished by the 

 much larger size of the calices and the total absence of septa 

 (PL VI., fig. 4). Milne-Edwards and Haime have separated 

 Alveolites Grayi from Alveolites Labechei, upon the ground that 

 " its calices are always larger, and are limited by walls that are 

 thicker in proportion to the size of the corallites." After a 

 careful examination, however, of both of these forms, I am 

 forced to come to the conclusion that they are not specifically 

 separable, the more especially as single specimens are not un- 

 common in which the calices have in parts the long diameter of 



