230 THE GENUS MONTICULIPORA. 



rently quite similar to the incomplete tabulse of forms like M. 

 frondosa, D'Orb., M. Nezvbcrryi, Nich., &c. I have not, how- 

 ever, succeeded in detecting any traces of these incomplete 

 tabulae in vertical sections, and the above interpretation is 

 therefore rendered uncertain. 



Tangential sections which pass at a little distance below the 

 surface, and which (owing to the curved surface on which the 

 corallum grows) cut the corallites obliquely, show the corallites 

 to be intersected with numerous complete tabulae (PI. III. 

 fig. \d). 



Vertical sections (PI. III. fig. 4^), if passing through the cen- 

 tral part of the expansion, show the short corallites to be 

 approximately vertical, and to be intersected by many hori- 

 zontal and complete tabulae. As before said, I have not been 

 able in the few sections which I have prepared to find any in- 

 complete tabulae, though tangential sections would lead to the 

 belief that such must exist in, at any rate, some of the tubes. 



As regards the affinities of this remarkable form, Mr E. O. 

 Ulrich refers it (Journ. Cincinnati Soc. Nat. Hist., 1879) to a 

 new genus, which he regards as referable to the Polyzoa, and 

 which he names Atadopora. This genus is defined as some- 

 times encrusting, sometimes ramose, composed of imperforate 

 tubes, the walls of which are supplied with pseudo-septa, which 

 may or may not be visible at the surface, and which are never 

 more than five or six in a single tube. Tabulae, if present, are 

 said to be complete, interstitial tubuli are " rather sparingly 

 developed," and monticules are usually present. With most 

 of the types which Mr Ulrich refers to Atadopora I have no 

 acquaintance ; but so far as Monticulipora {?) Ortoni is con- 

 cerned, I am unable to discover one of the most important 

 of the diagnostic marks above enumerated as characteristic of 

 the genus. I cannot, namely, recognise the "pseudo-septa," 

 which are stated to exist in the genus Atadopora. It is true 

 that the calices and visceral chambers of the corallites are 

 commonly indented by blunt inward projections ; but these are 

 not what I should call " pseudo-septa." On the contrary, they 



