HIPPOTHOA. 295 



"This species differs so decisively from the two pre- 

 ceding, that there can be no doubt of its being specifically 

 distinct. The cells are calcareous ; enlarged, and rounded 

 at the distal, and pointed at the proximal end. Their 

 direction is linear ; they are attached to each other at their 

 extremities, and their length is about four times their trans- 

 verse diameter." (i?. Q. CoucJi.) 



4. HippOTHOA Cassiterides, Couch. 



Hab. " On a stone betwixt the Scilly Islands and the 

 Land^s-end." "The cells are stouter and more pear-shaped 

 than in H. divaricata, and the threads of connection shorter 

 and stouter." "At a short distance from the proximal 

 lip is a small pearly tubercle, which is larger in one cell 

 than another." " This tubercle is very different from any- 

 thing ever observed in //. divaricataj and constitutes it a 

 distinct species." {R. Q. Couch.) 



Genus XI. GEMELLARIA, 8avigny. 



Gen. Char. Polypidom plant-like, sub-calcareous, rather soft 

 and flexible when dry, much branched dichotomously : cells 

 geminate, exactly opposite, united back and back with a thick 

 dissepiment, a joint above and below each pair. Polypes Asci- 

 dian, with elongated tentacula ; no gizzard. — Dr. Johnston. 



