GENERA OF FA VOSlTIDyE. 47 



half line in diameter, sometimes less, and often more. Calices 

 regularly polygonal, with thin walls, generally tolerably uniform 

 in size in any given specimen, but always having smaller and 

 younger ones intercalated among those of average size. Walls 

 of the corallites not thickened towards their mouths, sometimes 

 longitudinally striated on their flat faces, and furnished with 

 two (sometimes one or three) rows of mural pores on each 

 prismatic face. Pores alternately placed, surrounded by an 

 elevated margin. Tabulee complete, rarely inosculating ; some- 

 times incomplete and inosculating in parts of a colony, while 

 complete in others. Septa usually obsolete or irrecognisable, 

 sometimes represented by rows of tubercles or even by well- 

 developed radiating spines. 



Obs. — If the forms which I have here admitted under the 

 head of F. Gothlandica, be really referable to this form, then it 

 must be allowed that we have to deal here with one of the most 

 variable species of a variable genus. All the above, however 

 (with some others not included in this list), are clearly descen- 

 dants of a single stock, belonging to the same type-form, differ- 

 ing only in characters of comparatively trivial importance, and 

 for the most part insensibly passing into one another by the 

 intervention of examples possessing intermediate characters. 

 Some of the forms included in the series are so far distinct 

 that they may well retain distinct varietal appellations ; but 

 their general relationships are so close that I have thought it 

 best to collect them under a single specific title, rather than 

 to follow some high authorities in treating each as a separate 

 species. 



Favosites Gothlandica was originally described from speci- 

 mens found in the Wenlock Limestone of the island of Got- 

 land (Lamarck, loc. cit), and this name was restricted by 

 Milne-Edwards and Haime to forms occurring in the Silurian, 

 the species not being admitted as a Devonian one. We may 

 therefore properly regard the form which occurs so commonly 

 in the Upper Silurian of Europe, and which palaeontologists 

 have so lono- recognised under the name of F. Gothlandica, 



