1 84 THE GENUS MONTICULIPOKA. 



correct In his statement that the colony really grew parasitically 

 upon the closed and tapering extremities of the dead shells of 



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fG 



Fig. 37. — Monticiilipora- davacoidea, James. A, An average specimen of the natural size; 

 B, Part of the surface of the same, enlarged eighteen times ; c. Portion of a tangential 

 section, enlarged eighteen times ; D, Part of a transverse section of the same, show- 

 ing the corallites radiating outwards from the foreign body to which they are attached 

 inferiorly, enlarged seven times; E, Part of the same section, enlarged eighteen times, 

 showing the uniformly thin-walled corallites, and their few and lemote tabulae. From 

 the Cincinnati Group, Cincinnati, Ohio. 



OrtJiocerata. This is, therefore, a curious instance of the 

 persistence with which a particular species attaches itself to 

 some particular object, never seeming to fix itself upon any 

 other. 



Apart from its very peculiar and apparently constant form 

 and mode of growth, M. clavacoidca is readily distinguished by 

 its minute structure. Tangential sections (fig. 37, c) show that 

 the corallites are uniformly thin-walled and polygonal, slight 

 nodes being often formed at the angles of junction of contigu- 

 ous tubes. Their size is very uniform, though groups of coral- 

 lites of slightly larger dimensions than the rest are certainly 

 occasionally developed. In any case, there exists no series 



