110 



the great keel which springs from each branch internally. No cells are carried by the 

 areas formed by the anastomosis of contiguous branches 



I have only seen a single, very large and well preserved example of this genus, and 

 a careful examination of this has still left me entirely unable to elucidate and explain some 

 of the most extraordinary structural featuresw hich it presents. There can, however, be no 

 doubt as to the complete distinctness of the genus from any previously known. A compre- 

 hension of the very remarkable characters presented by this genus will perhaps be best ob- 

 tained from a detailed account of the different figures of the above illustration, all of which 

 represent different portions of the onfy known specimen. 



a. This figure exhibits a portion of the exterior of the frond, showing the fenestrules and 

 the outer non-celluliferous aspect of the branches. In the portion here illustrated of the na- 

 tural size, and partially shown at b on an enlarged scale, the fenestrules are oval, and arranged 

 in diagonal lines, and the branches are strongly keeled; the general appearance closely resem- 

 bling the non-celluliferous aspect of Retepom prisca (Goldfuss), and the fenestrules being 

 formed in the same way by the simple inosculation of the branches, without the development 

 of distinct dissepiments, c. This represents another portion of the exterior of the frond, 

 near the base, where the fenestrules are polygonal and are not arranged in regular diagonal 

 lines. In some cases, the fenestrules present the appearance of being closed by a delicate ex- 

 ternal membrane. 



d. This figure shows a small portion from which the outer non-celluliferous layer of the 

 branches has been stripped off, showing the proximal ends or bases of the cells, arranged in a 

 double inosculating row on each branch, and lying in the same plane as the fenestrules. 



e. This figure exhibits, on an enlarged scale, a small portion of the exterior of the frond 

 from which the outer non-celluliferous layer and the cells themselves have been stripped away, 

 leaving to view the circular mouths of the cells arranged in two alternating rows, which are 

 still in the same plane as the fenestrules, and which do not encroach upon the spaces formed 

 by the inosculation of the branches. 



/. This figure is a greatly magnified representation of a transverse section of the frond at 

 a point considerably removed from the base, showing the branches cut across. Above, the 

 branches are separated by the fenestrules, and immediately beneath this are seen the dark 

 oval spaces contained within the body of each branch, a pair in each, and representing the 

 cavities of the biserial cells. Below this, again, each branch is seen to give origin to an im- 

 mense vertical keel or ridge, which is directed inwards towards the interior of the frond. 

 These ridges are separated by deep intervening grooves ; and there can be doubt that the cells 

 open at the bottom of these groves, those of one side of the branch opening on one side of the 

 base of the great keel, and those of the other opening upon the opposite side of the same. 



g. This exhibits a greatly magnified transverse section of the frond at a point a little 

 above the base. As in the preceding, we can recognise without difficulty the shallow fenes- 

 trules, the divided branches carrying in their interior, each, a pair of cells, and the great inter- 

 nal keels. Here, however, we have two new features. Firstly, the deep grooves between the 

 keels are sub-divided by delicate calcareous laminae which connect the opposite side of contigu- 

 ous keels, and divide the intervening grooves into shallow transverse chambers. Secondly, the 

 grooves between the keels are closed internally by a continuous calcareous membrane, which 

 has a minutely porous or vesicular structure. 



h. This exhibits a fragment taken from near the base, and showing the internal surface. 

 We see here the inner faces of the great longitudinal keels, separated by shallow grooves which 

 are filled up by a continuous calcareous membrane, which is not penetrated by either the 

 fenestrules or the cells. No apertures, therefore, of any kind appear on the interior of the 

 frond near the base. In the upper portion of the frond, however, a fragment of the interior 

 exhibits simply the great keels with deep intervening grooves, and the layer connecting the 

 keels cannot be distinctly made out. At the right hand corner of h, the keels and their con- 

 ne^ing membrane are broken away, and we see the cavities of the rows of cells ; whilst the 

 extreme corner is still further broken away, so that the fenestrules comes into view. 



i. This simply represents a single branch in transverse section, greatly enlarged, and 

 shows the cells in the interior of the branch, and the great triangular keel proceeding from its 

 internal surface. 



From the above description, it will be evident that the structure of Carinopora is quite 

 anomolous, and wholly unlike anything that has been hitherto observed in any member of the 



