44 



Genus FAVOSITES (Lamarck). 



The genus Favosites (Lamarck), comprises branched or massive corals, composed of numer- 

 ous more or less polygonal corallites, which are divided internally by transverse partitions or 

 "tabulae," sometimes quite rudimentary. The walls of the corallites are perforated by one, 

 two, three, or more rows of " mural pores," by which the separate corallites are placed in 

 communication. The septa are absent or rudimentary, being at most represented by tuber- 

 cles or short spines. 



The generic limits of Favosites have not been universally agreed upon by palaeontologists, 

 and the genera JEmmonsia, (Edw. and H.), and Astrocerium (Hall), have been founded upon 

 differences which Mr. Billings rightly regards as not of generic value. Thus, JEmmonsia is 

 distinguished from Favosites simply^ by the incompleteness of the tabulae ; but this same 

 peculiarity can sometimes be observed even in F. Gothlandica, the type-species of Favosites, indi- 

 vidual examples of which not very uncommonly exhibit portions with the complete tabulae of 

 Favosites and other portions with the imperfect tabulae of Emmonsia. In the same way, there 

 ; are many examples of Favosites, of more than one species, in which the tabulse, whether natu- 

 rally or from some peculiarity in the manner in which they were preserved, are quite rudi- 

 .mentary and are even more imperfect than they are in ordinary specimens of Favosites hemis- 

 pherica, upon which the genus Emmonsia was founded. 



The genus Astrocerium, again, was founded by Hall (Pal. New York, Vol. 2, p. 120,) to 

 include corals exceedingly like Favosites in all superficial characters, but differing in the pos- 

 session of spiniform septa. It would appear, also, though this character is not specially 

 mentioned, that Hall believed the corals which he referred to Astrocerium to be destitute of 

 mural pores. This latter point, if it could be proved, would amply suffice to separate Astro- 

 cerium generically from Favosites ; but there is much reason to think that the apparent absence 

 of mural pores may be due to mineralisation merely. At any rate, it is far from uncommon 

 to meet with examples of undoubted species of Favosites in which no pores can be detected. 

 The other point namely, the presence of spiniform septa is also not a satisfactory distinc- 

 tion, partly because some examples of Favosites exhibit the same thing, and partly because 

 some examples which would generally be referred to Astrocerium. from their geological position 

 . and general appearance, are without any traces of septa. Upon the whole, therefore, it would 

 appear that the genera Astrocerium and Emmonsia can not be retained. 



The numerous species of Favosites may be divided into two groups, according as they are 

 massive or ramose, F. Gothlandica being the type of the former, and F. polymorpha of the 

 latter. The characters which have been relied on as separating the species of this genus are 

 chiefly the following : 1. The diameter of the corallites ; 2. The equality or inequality in 

 size presented by the corallites ; 3. The completeness or incompleteness of the tabulae ; 4. The 

 number of rows of mural pores ; 5. The position of the mural pores, whether on the flat faces 

 of the polygonal corallites or on their angles ; 6. The presence or absence of rudimentary 

 septa. For convenience of reference the more important species of Favosites may be arranged 

 as in the following table, it being remembered that some of the species here enumerated, are 

 perhaps not valid, and the characters derived from the number of rows of mural pores are not 

 .constant, even in the limits of the same species : 



A. MASSIVE SPECIES. 



a. Tabulaa complete. One row of mural pores, placed on the faces of the corallites. 



1. Favosites basaltica (Gold). 



2. Favosites turbinata (Billings). 



b. Tabulae complete. Two rows of mural pores, placed on the faces of the corallites. 



3. Favosites Gothlandica (Lam). 



4. Favosites Niagarensis (Hall). 



c. Tabulae complete. Three rows of mural pores, placed on the faces of the corallites. 



5. Favosites multipora (Lonsd). 



6. Favosites Troosti (Edwards and Haime). 



d. Tabulae complete. Mural pores situated in the angles formed by the prismatic walls 

 /of the corallites. 



7. Favosites alveolaris (Gold). 



8. Favosites aspera (D'Orb). 



