CTIISIA. 281 



broadest patches I had ever seen; there was much of the 

 shell covered with HippotJwa catenulata, much larger in 

 size than I had ever met with it before ; there was one spe- 

 cimen of Hippotlioa divaricata j one of Alecto gramdata ; 

 several ai Alecto major, and three or four oi Alecto dilatans ; 

 one of what we thought was Pustulijoora defiexa, and many 

 fine specimens of Llastopora ohelia ; and as these were 

 located alongside of Alecto major and Alecto dilatans, they 

 were, at a single glance, seen to be so different, that I should 

 never have thought of comparing them. Alecto major and 

 Alecto dilatans may run into each other, but Diastopora 

 ohelia, in its pretty, continuous, unbranched scurf, is evi- 

 dently, I humbly think, different from any of the three species 

 of Alecto. 



Family CEISIAD^. 



Character. Polypidoms phytoidal, jointed, dichotomously 

 branched ; the cells tubular, disposed iji one or two series, with 

 the circular apertures alternately looking to opposite sides. — 

 Johnston. 



Genus VI. CEISIA, Lamoitroux. 

 1. Crisia eburnea, Ellis. (Plate XV. fig. 52.) 



