156 MADREPOR AEI A. 



perforate, very zigzag, sometimes forming a delicate angular, but opeu-meshed, reticulum when 

 seen from above. The 24 septa are very tlrin, and the primaries and secondaries meet in a 

 large open columellar tangle. The tertiaries appear to end freely. 



There is only one specimen, silicified throughout, and with the coral imbedded in the clear 

 matrix. But there are reasons to doubt whether the original conditions have been preserved, 

 and also whether it is a Goniopora at all. The thin zigzag walls and the septa are nowhere 

 sharply defined when seen under a pocket-lens, and what appear to be the apertures in the 

 walls have ragged irregular outlines. It looks as if the substance of the coral skeleton had 

 been etched away ; and, if so, there is a possiliility of these apertures being secondary and 

 accidental, and this alone would rule the specimen out of this genus. It is also characteristic 

 of the Poritidie that the bases of the calicles fill up with tissue so as to be only occasionally 

 traceable through the corallum. Here they are long open tubes. Then, again, it is very rare 

 to see the tertiary septa end freely, and, as a rule, it is not like Goniopora to have such rigid 

 septa. There is a fluency in the skeleton of this genus, with hardly a single exception, which 

 is in great contrast to the skeletal rigidity shown in this fossil ; such subtle indefinable 

 distinctions are often excellent guides. But even in the face of these difficulties we have to be 

 true to oixr morphological analysis ; and from this point of view I think that, on the whole, 

 the balance of the direct structural evidence is in favour of its being a Goniopora : the thin 

 zigzag membranous walls, occasionally forming a reticulum, the large columella, the 24 septa, 

 are all so much positive evidence, while the existence of the pores in the walls points also in 

 the same direction. The difficulties can perhaps be regarded as mere questions of degree. 



The specimens belonging to the Geological Society are from the " Marl formation, the 

 Inclined Beds and Chert" of Antigua, and from "the Silt of the Sandstone plain," San 

 Domingo. They were placed by Duncan in the genera Steplmnocoinia and EJiodarwa ; with 

 the former identification I cannot at all agree. 



a. Geol. Dept. 1298. 



Group XIV.— FORMS WITHOUT RECORDED LOCALITY. 



On the method of designating such forms. 



Forms without recorded locality present us with morphological facts which we cannot 

 ignore. They cannot take their places in the geographical series, and hence cannot be de- 

 signated by any geographical names. By using the letters of the alphabet to indicate the 

 uiiknown locality, we can designate them sufficiently for purposes of reference. The letter x 

 may stand for the country, and a, h, c, etc. for the other details. Goniopora x a, x b, x c, would 

 mean members of the genus of whose locality we know absolutely nothing. If, however, the 

 country is known but not the district, we can write Gonioj^ora Aiistralia a, Goniopora 

 France a, b, c, etc., as we have already had to do on pages 64 and 145. In this final group we 

 have no information whatever as to the localities of the specimens, and yet their morpho- 

 logical characters are of great interest — the interest in them indeed continues to increase the 

 closer the many variations on the primitive type are studied. 



In two cases (see Goniopora x b and x c) we have been able to suggest localities, our 

 reasons being based solely upon morphological comparisons. 



