52 



THE GENUS MONTICULIPORA. 



occurs in forms like Faiwsites hemisphcErica, Yand. and Shum.) 

 In some members of the genus, however, we have a quite 

 pecuHar form of " incompleteness " of the tabulse, such as I 

 have never observed in any example of the Favositidce. In 

 the species alluded to (namely, M. Newbei'-ryi, Nich., M. Scl- 

 wynii, Nich., M. frondosa, D'Orb., M. Cincinnatiensis, James, 



AL vwlesia, Nich., &c.), the large 

 corallites are provided with a re- 

 markable double tabulation, which 

 produces appearances quite readily 

 recognised both in vertical and 

 tangential sections. When exam- 

 ined in longitudinal sections (fig. 

 7, a), the principal tabulse of each 

 large tube are seen to form a row 

 of lenticular vesicles on one side of 

 the visceral chamber, each tabula 

 being curved in such a way as to 

 B, Part of a tangential section of the joi^ inferioHy with the tabula uext 



same, similarly enlarged, showing the 



characteristic appearance produced by beloW it in the SerieS. On the 



these incomplete tabulre, when the tU l J ...u ^' r >.i 



corallites are transversely divided. ^ther hand, the portlOU of the VIS- 



ceral chamber not occupied by the 

 lenticular vesicles just spoken of, is usually intersected by a 

 moderate number of horizontal plates, which pass from the 

 vesicles on one side to the opposite wall. When examined in 

 tangential sections (fig. 7, b), these peculiar vesicular tabulae are 

 seen to extend round about two-thirds of the circumference of 

 the visceral chamber (or sometimes to encircle it), terminating 

 internally, or on the face turned towards the axis of the tube, 

 in a concave free margin. Hence, in tangential sections their 

 cut edges are seen to form deeply curved lines enclosing an 

 excentric tube on one side, or rarely in the centre, of each 

 of the large corallites ; while the horizontal plates which 

 complete the tabulation of the tubes are necessarily not 

 exhibited at all. 



Fig. 7. — A, Long section of two large and 

 two small corallites of Montiailipora 

 Sehvynii, Nich., enlarged eighteen 

 times, showing the peculiar incom- 

 plete tabulffi of the large corallites ; 



