140 MADREPORAKIA. 



The calicles arc frequently flush with the surface, very small, ranging from 1 ■ 5-2 mm., 

 polygonal to the naked eye. The wall when thin is very inconspicuous, there being no con- 

 tinuous wall-thread traceable round the calicles, usually irregular skeletal tissue separates 

 calicle from calicle, either thin with very few pores, or thick and with many pores like a 

 reticulum, and it is then raised slightly as a low ridge. The pores in the top of the wall 

 are specially minute. The septa, about 20 in number, are not quite radially symmetrical. 

 When the wall is thick and reticular they are very thick near the wall and taper inwards, 

 often irregularly moniliform. The directives are long and sometimes form a continuous keel 

 across the calicle; on each side of this, symmetrical portions of the typical formula may 

 sometimes be seen. Many of the septa seem to start forking just as they reach the wall. 

 While their top edges are smooth and rounded, their sides are roughened by very thin 

 incipient synapticulae. The interseptal loculi are narrow and slit-like. The columellar 

 tangle varies in size, the thickened tips of the septa either fusing or joined by exquisitely 

 delicate synapticuhe, in strong contrast with the thick septa which they unite. When the 

 wall is slightly raised, the pali formation is typical, slightly raised thickenings appearing on 

 the columella at the points of fusion of the septa. 



In section, the texture is composed of nearly straight trabecular densely crowded together, 

 with only small pores between them. 



There are three specimens of this coral from Auvers, differing slightly from one another, 

 and a fourth from some unknown locality in France. The specialisation appears to differ 

 entirely from that of any Goniopora yet described, but in reality the septa appear to be 

 lamellate and essentially of the same character as those of the last two forms. It is not 

 impossible that the closeness of the skeleton, the small size of the slit-like interseptal loculi, 

 these being still further closed by the synapticulfe, may be adaptations to meet the danger 

 from sand here so often alluded to (see Remarks, p. 145). 



This is another of the French Goniopores which might be taken at first sight to be Pontes. 

 We have already described Goniopora Gironde 1 and G. Dax 4- All three can be distinguished 

 from Porites by the forking of the septa near the walls. In none of them can we find true 

 transition forms, because, as shown in the Introduction, the septal formula of Porites can be 

 deduced from that of Goniopora by a reduction of the tertiaries according to a regular 

 pattern. This regular pattern is not seen in any of these, the reduction being qxiite irregular 

 and generally obscuring the typical arrangements. 



Of the three specimens from Auvers, one has exclusively thick walls, while both thick 

 and thin can be found on the other two. There is no mistaking the characters of this coral, 

 the comparatively speaking thick, irregularly moniliform septa, and the fine synapticulae, 

 mostly as teeth, but, nearer the columellar tangle as definite bars, which help to form the 

 tangle. The paliform swellings are only seen on the specimen with thick walls. 



The fourth specimen is probably from the same locality. It has thin walls and is flat and 

 encrusting. There is no mistaking the similarity in general character. 



a.-c. Geol. Dept. R. 55,680. 



d. „ „ 11.4824. 



