FRENCH GONIOPORCE. 145 



very straggling, seldom continuous round a calicle, merely indicating the irregular polygonal 

 boundaries between the calicles. The septa, 13-14, forking in twos and threes near the wall, 

 are very irregular, and bent in all directions so that the radial symmetry is greatly obscured. 

 The curling septa meet irregularly in the centre, forming a large, ill-defined columellar tangle. 

 The vertical section is built up of straight nodulated trabecular, rather stout, but separated 

 by rows of pores of about equal diameter with the trabecular. Immense numbers of tabulae 

 are developed. 



This remarkable specimen, without recorded locality, has the habit of a Porites, but is 

 placed in this genus for the following reasons : — a. There are, generally, one or two more 

 septa than in Porites, i. e. 13-14 instead of 12 ; b. The septa fork near the walls, which 

 suggests a reduction of the typical formula of Goniopora (see Introduction, p. 21), and there 

 is no resemblance whatever to the septal formula of Porites ; c. There seem to be indications 

 of a columellar tangle, which is not common in Porites. Any one of these reasons would have 

 been sufficient, but the three together leave no doubt in my mind as to the correctness of 

 placing the coral here. 



The specimen is remarkable because it is one of the two Gonioporce with the smallest 

 calicles yet described (see p. 183). It is unfortunate that its locality is unrecorded. 



Comparing it with other known French Gonioporce, it may either link on with such 

 forms as G. Gironde 1 or G. Box 4, which latter also has very minute calicles, or with 

 G. Paris Basin 11 and 12. The boring molluscs, apparently of the genus Thylacodes, secreting 

 calcareous tubes with conspicuous hemispherical diaphragms, which burrowed through it, are 

 known both in the Eocene of the Paris Basin and in the Aquitanian beds of the districts near 

 Dax. Our suggested locality and horizon for this coral are purely provisional. 



a. Geol. Dept. R. 957. 



Remarks on the French Forms. 



The figures and descriptions show clearly that the Gonioporce of the Paris Basin were, with 

 few exceptions, very highly specialised. The primitive type of calicle described in the 

 Introduction, with its tendency towards fluency as opposed to the rigid symmetry of the great 

 bulk of the Madreporarian corals, reached an extreme in this direction in these remarkable 

 fossils. I know of no Madreporarian showing such developments of flaky and filamentous 

 networks as those shown, for instance, in PI. X. fig. 5 and in PL X 6 . fig. 2. 



The great majority of them were evidently small colonies, and their larvse seem to have 

 been compelled to find precarious footholds on a sandy bottom. Many seem to have been 

 attached to weeds, which is still a common occurrence with recent small-calicled forms (e. g. 

 Porites) ; others to shells and small pebbles. This was also the case with their congeners 

 whose remains are now found in the Bracklesham Bay of Sussex. 



The number of small forms alone, in a genus which consists typically of reef corals and 

 produces large colonies, is enough to suggest an unfavourable environment. Knowing as we 

 do, from the beds in which they are found, that they mostly grew on sand or mud, we need 

 not postulate any disadvantageous climatic conditions ; for these two forms of the sea-bottom 

 are, of all others, the most inimical to coral growth. 



u 



