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ME. A. WILMORE ON THE CARBONIFEROUS [NOV. 1 9 10, 



fossula, and sometimes traces of three other fossilise. The cardinal 

 fossula is, at first, bounded by two short irregular thickened septa. 

 Later on, a short cardinal septum appears, and as this grows in 

 length the enclosing septa open out, the whole appearance of the 

 fossula being decidedly Caninoid. The cardinal fossula is barely 

 traceable in the cylindrical Amplexoid stages. 



There is nothing like uniformity in the development of the 

 cardinal septum and its fossula as seen in different examples, and 

 the development of the other fossulae is exceedingly variable. 



Fig. 5. — Variations in form o/Zaphrentis amplexoides, sp. 



nov. 



[The figures are about two-thirds of the natural size.] 



Sometimes one alar break is quite conspicuous, without the other 

 being more than barely perceptible. Sometimes a counter fossula 

 is quite obvious ; while at other times there is little to distinguish 

 even a counter septum. I have not been able to discover any rule 

 in the appearance and disappearance of these fossulae. 



With respect to the septa generally, they are usually much 

 thickened, especially in the cardinal quadrants, in the earlier stages 

 of growth. They are sometimes remarkably irregular in direction, 

 the free ends in the Amplexoid stage being often bent in a capricious 

 fashion. There is rarely the square-cut end noticed in some species of 

 Am-plexus. Some of these irregularities in the direction of the septa 

 are well seen in the sections figured : one specimen, however, shows 



