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H. N. MOSELEY. 



contain the single pair of long mesenterial filaments. These 

 elongate chambers are invariably in the same position in all the 

 polyps, being the right and left median lateral chambers, and the 

 mesenteries bearing the filaments are the ventral ones of each of 

 these pairs. They fit in the recent state hito two very deep conical 

 pits formed in the floors of the interseptal spaces between the 

 calcareous septa, which are disposed second and third, right and 

 left, from the median inferior or ventral septum. This pair of 

 conical pits in each calicle is extremely deep, and after the 

 corallum has been treated with acid for some time, and all other 

 traces of the calicles have been dissolved away, the pairs of pits 

 remain conspicuous, still disposed in rows all over its surface. 

 The pits are situate in the inferior or ventral region of each 

 calicle, just inferiorly to its shorter diameter. The calicles are 

 all disposed, as is well known, with their longer axes parallel 

 to the lengths of the branches. Each calicular cavity is divided 

 by a median plate or ridge along its long axis into two halves. 

 Passing to this plate, which has been regarded as an elongate 

 columella by Milne Edwards, from the margins of the calicle arc 

 three pairs of septal ridges, disposed right and left, which divide 

 up the two halves of the area of the calicle into an irregular series 



Diagram, showing the arrangement of the septa in Seriatopora a, 

 superior or dorsal extremity of the calicle ; b, inferior of ventral ex- 

 tremity ; c c, smaller rudimentary septa ; d d, mouths of the pits 

 which contain the pouches with the mesenterial filaments. 



of chambers, the arrangement of which in the superior or 

 dorsal region differs very much from that in the inferior. Two 

 further pairs of ridges, which are small and almost rudimentary. 



