GENERA OF CH^ETETID^E AND MONTICULIPORID^E. 267 



throughout, and which, though somewhat unequal in point 

 of size, are not divisible into a series of larger and smaller 

 corallites. Transverse and longitudinal microscopic sections 

 (PI. XII., figs. 4 and 4 a) show that the walls of contiguous 

 corallites are absolutely and uniformly amalgamated, so that 

 no traces whatever can be detected of the original divisional 

 lines between them. The walls are thick, and the most care- 

 ful examination both of actual specimens and of thin sections 

 has failed to produce any evidence of the existence of mural 

 pores ; so that we must accept the view held by all the older 

 observers of this species as to the imperforate condition of the 

 walls of the corallites. The calices, like the corallites, are un- 

 equal in point of size, though in no uniform manner, and com- 

 monly exhibit an inward tooth-like projection (PI. XII., fig. 4 b] 

 on one side, sometimes with a similar but smaller correspond- 

 ing process on the opposite side of the tube. These tooth- 

 like projections are never present in more than a quite limited 

 number of the tubes, and they vary much in length ; while 

 transverse sections (PI. XII., fig. 4) show them to be pro- 

 duced by the existence of a vertical lamella or longitudinal 

 inflection of the wall of the corallite. Their true nature was 

 pointed out by Lonsdale (loc. cit.}, who maintained that they 

 were due to the uncompleted fission of the old tubes, the fissi- 

 parous mode of development being characteristic of the species. 

 The correctness of the views of Mr Lonsdale upon this point 

 has subsequently been upheld by Mr R. Etheridge, jun., and 

 myself (Journ. Linn. Soc., vol. xiii. p. 366). The tabular 

 (PI. XII., fig. 4 a) are always numerous, and are invariably 

 complete and horizontal ; and Milne-Edwards and Haime are 

 perfectly right in asserting (in their description of the genus 

 Chcetetes} that they are not uniformly placed at corresponding 

 levels in contiguous tubes. At the same time Mr Lonsdale is 

 correct in his assertion that the species possesses " diaphragms 

 in parallel bands ; " for the tabulae are specially developed peri- 

 odically, at the same level in all the tubes, so that the corallum 

 is conspicuously composed of a succession of concentrically dis- 



