THE GENUS ALVEOPOEA WITH THE EAVOSITIDiE. 501 



these cases the epifcheca changes its function ; it ceases to be 

 mural and becomes pellicular, coveriug over the basal calicles as 

 they progressively die. It is worth noting that this pronounced 

 epithecal pellicle can at any time resume its original functions, 

 bending outwards and forming part of the walls of new buds. 



In the formation of these colonies ifc must be noted that the 

 skeletal walls of the calicles not in contact with the mural (as 

 opposed to pellicular) epitheca are, as above maintained, purely of 

 septal origin, while those round the periphery have part of their 

 walls formed by the epitheca. 



As the colony grows in height, the living polyps rise in the 

 ealicle-tubes, and their free bases often secrete "tabulae." The 

 rising may be practically simultaneous over the whole colony, in 

 which case a tabulate plate will run more or less continuously 

 through the whole colony (see Savigny's figure of ^. doddalea and 

 Dana's of his A. s])ongiosa). 



Payosites. 



Nearly all the characters above described for AUeopora apply 

 equally well to the Palseozoic genus Favosites. Very young 

 colonies have been described and figured by Hall {cf. Indiana 

 Gaol. & Nat. Hist., 11th Eeport, 1881, p. 229, pis. 1 & 3), by 

 Milne-Edwards and Haime (British Eossil Corals, p. 185, pi. 60), 

 and by Nicholson (Palteozoic Tabulate Corals, 1879, pi. i. fig. 3), 

 although none are quite so young as the oldest here figured 

 (PL 33. fig. 3). Prom these we see the same prominent epithecal 

 cup and the same early obscuration of the parent polyp. Indeed, 

 all the general characters of the colonies, young and old, appear 

 to be the same — the polygonal calicles, their thin walls, the 

 mural pores, and the spiny septa. Lastly, the method of budding 

 appears also to have been the same, as v. Koch, who has published 

 sections of the two for comparison, admits *. Before, however, 

 this last point can be established, it is necessary to discuss the 

 character of the walls between the polyps of a Favosites colony. 



From all the ordinary descriptions of Favosites we gather that 

 each calicle has its own distinct wall, but that these walls are 

 intimately fused together by the crowding of the calicles, which 

 is so close that they press one another into polygonal prisms. 



* Compare ' Pal^ontographica,' xxix, p. 329 (1883), with Morph. Jahrb. xxiv. 

 1896, p. 167. 



LIKN. JOUKN. — ZOOLOGY, VOL. SXTI. 36 



