STOMATOPORA GRANULATA. 425 



or free at the extremities, or giving off erect processes ; 

 simple or branched; branches more or less ligulate. 

 ZCXECIA in great part immersed, arranged in a single series 

 or in several, which take a linear direction or are very 

 slightly divergent. 



THE distinction between this genus and Tubulipora is 

 somewhat shadowy. In classifying the Cyclostomata we 

 have to base our divisions mainly on habit or mode of 

 growth, on the plan according to which the zorecia arc 

 aggregated together into colonies ; the simplicity and 

 general similarity of the cell throughout the tribe leave 

 no other course open to us. We have to deal with very 

 uniform structural elements very variously combined ; and 

 the modes of combination chiefly supply us with the bases 

 of our system. Under these circumstances, we may not 

 expect very strongly marked boundary lines. Stomato- 

 pora is distinguished by its linear, adpressed, dichoto- 

 mously branched zoarium, in which the cells are generally 

 immersed for a great portion of their length, and are not 

 divergent, except in a very slight degree, and then almost 

 exclusively towards the very extremity of the branches. 

 The most marked variation within the limits of the genus 

 is found in the forms which have the zoarium partially 

 free and erect. They constitute the subgenus Proboscinu 

 of Smitt. 



a. Zoarium entirely adherent. 

 STOMATOPORA ORANULATA, M. -Edwards. 



Plate LVII. fig*. 1. -'. 



ALEC TO (iUAMLATA, M.-Edward, M&u. 13, pi. xvi. figs. 3, 3fl: Johns! . 

 (part.), B. Z. ed. 2, 280 (pi. xlix. figs. 1, 2, are prubabK 

 referable to 8.Johnt<Mi): Busk, B.M.Cat. iii. 24, pi. xxxii. 



