2 G. HERBERT FOWLER. 



3-5 mm. in diameter. Branchlets small and short, about 1-2 cm. 

 in length, consisting generally of a few thin and long tubiform 

 calicles ; towards the apical parts of the branches they become much 

 less elongated and often quite short. Surface slightly porous, very 

 distinctly costulated throughout, and marked with fine echinulations 

 which are very distinctly arranged on the calicles. Calicles generally 

 tubiform, about 1*5 mm. wide and 1 cm. long, except towards the 

 apical parts of the branches, where they are shorter and smaller, and 

 sometimes tubonarif orm ; a few short tubonariform calicles are 

 generally placed on the surface of the branches between the branch- 

 lets. Star distinct, of six more or less lamelli-spiniform septa, two 

 of which, the distal and the proximal, are usually much enlarged, 

 and meet one another, often deep down in the fossa ; while 

 occasionally, as in the terminal calicles, the six septa are sub-equal, 

 and coalesce at the centre." 



" This species seems to be distinguishable from M. echinata 

 (Dana) simply by the costulations of the surface, which in the latter 

 is smooth or finely granulated. It is doubtful, however, whether 

 this character will prove to be sufficiently constant to separate the 

 two species, when a larger number of forms has been examined." 



Figs. 1 and 2 represent the dorsal and ventral aspects of a fragment 

 of a branch, and show most of the characteristics mentioned in the 

 above description. 



In a transverse section of the corallum (Fig. 3), the peripheral 

 ring of polyp cavities is cut somewhat obliquely (a a), owing to the 

 inclination of branchlets and calicles to the branch ; while the more 

 central ones, cut at a lower level and more transversely, are approxi- 

 mately circular in outline (a' a). They lie, roughly speaking, on 

 three sides of the branch, none are apparent on the fourth. The 

 shorter radius of the latter seems to imply that the growth in 

 diameter of the branch depends upon the outward growth of the 

 polyps. 



In the axis of the branch is a central cavity {ex.), into which project 

 six septum-like ridges ; this probably represents a cavity previously 

 inhabited by the now apical polyp. The tops of both my specimens 

 having been broken off, I have not been able to prove this ; nor 

 again to investigate the method of budding ; but in M. aspera is such 

 another central cavity with six septa, which is continuous with that 



