220 PEOr. H. A. NICHOLSOK AND DE. J. MrRIE ON THE 



The only coral which occurs in the same strata, and which 

 presents any resemblance to the tubes of Caunopora, is Si/ringo- 

 pora ; and we most freely admit that there is a singular resem- 

 blance between the two. Microscopic sections of Caunopora 

 show, however, that its tubes want all the characteristic internal 

 structures of Syringcpora ; so that we must provisionally conclude 

 that we have to deal here with a structure really belonging to the 

 Stromatoporoid, and certainly sufficient to warrant its generic 

 separation from Stromatopora. 



The range of Cauno]pora^ so far as we can speak ourselves, is 

 exclusively Devonian. 



(c) CLATnEODiCTTON, Nich. & Murie. 



Skeleton (" sarcodeme ") massive, closely resembling Stromato- 

 pora in superficial aspect and general appearance and structure, 

 but differing in the fact that the concentric laminae are minutely 

 undulated, and inflected at short intervals, so as to give rise to 

 successive layers of oval or rounded cells or vesicles, which are 

 usually distinct, but at other times open into one another by the 

 imperfection of their lateral boundaries. There are thus no 

 "radial pillars" as independent structures; but their place is 

 taken by partial or complete inflexions of the horizontal laminae 

 bounding the interlaminar spaces, which are bent in such a way 

 as to divide the space into complete or incomplete oval compart- 

 ments. Horizontal section simply reticulate. Surface tuberculate. 



Type. — ClatJirodictyon vesiculosum, Nich. & Murie. 



Geological Banye. — Upper Silurian and Devonian. 



[Though it is no part of the object of the present paper to enter into the 

 characters of species, we may as well append here brief specific diagnoses 

 of the only two forms of this group known to us, both of which are new.] 



Clathrodictyon vesiculosum, Nich. & Murie. 



Spec. char. — Skeleton in the form of cake-like expansions, from three 

 inches to a foot in diameter, one to two inches in thickness centrally, 

 but thinning out towards the circumference. Upper surface irre- 

 gularly undulating, and exfoliating concentrically round the elevated 

 points. Surface smooth. Internal structure of exceedingly fine and 

 close-set horizontal or slightly undulating laminae, of which about 

 twenty or twenty-five occupy the space of one line (counting in the 

 intervening interlaminar spaces as well). The interlaminar spaces 

 divided into minute lenticular cells formed by curved inflexions of 

 the horizontal laminae. 



