Cellepora and Paljthoa. 419 



that they rested on the ground, while in the other specimen 

 they are all simply rounded, like that of fig. 2, h. The same 

 remarks apply to the shell on which the Pglythoa had built 

 its structure as to that of Cellepora senegamhiensis^ excepting 

 that it appears to have been still more depressed, and, from the 

 smooth shining surface of the portion remaining in the inte- 

 rior, as exposed by a section of the uuillustrated specimen, 

 registered 12. 3. QS. 4, together with the elliptical aperture, to 

 have been one of the Naticidai. 



General Ohservations. 



The specimens from which the above descriptions have been 

 taken belong to the Liverpool " Free Public Museum ;" and 

 there are two of each, so that I have had one of each to sec- 

 tionize for the internal structure, while the best of each has 

 been retained entire for illustration, which, together with the 

 sections, will henceforth be returned to the museum for refer- 

 ence. The most remarkable part about them in a physiogno- 

 mical point of view is that organisms so widely separated in 

 the animal scale should, in the same locality, viz. the Sene- 

 gambian coast, present the same peculiarities of growth, 

 which, so far, appears not to have been noticed in any other 

 part of the world. There are two specimens of Cellepora 

 senegambiensis in the British Museum ; and 1 think that I 

 have seen it figured in some old work, but cannot remember 

 where. 



EXPLANATION OF PLATE XVI. 



Fi(j.\. CcUepora seneyamhieyms, n. sp. Zoariiim, natural size, a, hole 

 representing the aperture of the shell on which the zoariuin has 

 been built; hb, coloured portions on the surface; i', section 

 of an arm, showbig the same in the interior ; c c c c, group of 

 cells or zooicia, with their accompaniments, all maguitied on the 

 scale of l-48th to l-l80Uth inch ; del d d, oritice ; e e c ee, avicu- 

 laria ; /, ooecium ; (j //, rostrum ; /*, front view of rostrum «fec., 

 more magnified, viz. on the scale of l-48th to 1-OOOOth, inch ; i, 

 sinus of orifice ; k, orifice ; /, front part of cell or zorecium ; m, 

 orifice and sinus closed by operculum, and «, avicularium, on 

 the same scale ; o, diagram (on the same scale) to show calca- 

 reous granulations in p, ?-pellicle, on some parts of the zoarium ; 

 q, surface without the granular growth ; r, circidar diaphrag- 

 matic hole in the interstice ; s, tubercles on the border of the same ; 

 t, operculum covered with the granular gi'owth ; u, branched 

 structure in relief on the zocecium ; v, diaphragmatic hole in the 

 interstice. 



Fig. 2. Pahjthoa senegamhiensis, n. sp. : lateral view, with part of upper 

 surface (nat. size), a, polyp-cells ; b, rounded end of arm ; c, 

 section of the cylindrical part of the arm, to show position and 

 relative size of polyp-cells. 



Fig. t5. Pali/thoa senegambicnsia, n. sp. : under surface (nat. size). «, 

 orifice representing the aperture of the sliell on which the poly- 

 parv has ijeen built : b, fiatteiied end of arm. 



