MARINE POLYZOA. 27 



Brit. Zooph. 291 . pi. 38. figs. 3, 4 ; Couch, Zooph. Cornw. 57 ; 



Corn. Faun. iii. 127. pi. 23. fig. 3; Reid, Ann. $ Mag. Nat. 



Hist. xvi. 385; Johnst. Hist. Brit. Zooph. ed. 2. p. 337. t. 58. 



figs. 3, 4. 

 Cellaria reptans, Ellis and Soland. Zooph. 23; Lamk. Anim. s. 



Vert. ed. 2. ii. 191 ; Johnst. Trans. Newc. Soc. ii. 262. 

 Scruparia reptans, Oken, Lehrb. Nat. 90. 

 Crisia reptans, Lamour. Corall. 60 ; Templeton, Mag. Nat. Hist. 



ix. 469. 



Bicellaria reptans, Blainv. Man. (TAct. 459; Cuv. R. A. III. t. 

 Acamarchis Geoffroyi, Audouin, Expl. i. 241 ; Savigny, Egypt. 



pi. 11. fig. 4. 



Scrupocellaria reptans, Gray, Brit. Rad. 112. 

 Hab. Britain (ubique). 



5. EMMA. 



Cells in pairs or triplets. Opening more or less oblique, sub- 

 triangular,partially filled up by a granulated calcareous expansion. 

 A sessile avicularium (sometimes absent) on the outer side below 

 tbe level of the opening. 



Emma, Gray, Dieffenb. N. Zealand, ii. 293; Busk, Voy. Rat- 

 tlesn. 1. 3/3. 



This genus appears to be a natural one, though apparently 

 allied to Tricellaria (Fleming). The more important points of 

 distinction consist in the conformation of the opening of the cell, 

 and in the position of the avicularium when the latter organ is 

 present. The lower half of what would otherwise be the oral 

 opening of the cell is filled up by a thin plate of calcareous matter, 

 granulated on the surface, and by which the actual opening is 

 rendered more or less subtriangular, the mouth being placed just 

 below the apex of the triangle. The margin of the opening is 

 considerably raised, especially at the oral end, so that the opening 

 appears to be situated in a deep depression. This character of 

 opening, however, occurs also in a triserial species of Cellularia 

 from Algoa Bay. The position of the avicularium, entirely 

 below the level of the opening on the outer side of the cell, is the 

 peculiar characteristic of Emma as distinguished from Menipea, 

 in which that organ when present is placed in the upper and 

 outer angle, as in Cellularia proper and Scrupocellaria. It is 

 worthy of notice, that avicularia may be present in every cell in 

 some specimens, and most usually, whilst in others of equal size 

 there will be none at all apparent. So that the position of 

 these organs in this genus, as well as in others, is of more im- 

 portance systematically than even their existence. 



c2 



