,82 THE GENUS MONTICULIPORA. 



more strongly marked series of diagonals formed by the walls 

 of the tubes themselves. Similar, but less conspicuous and 

 less regular, divisional lines are visible in the calcite which 

 fills the tubes of the corallites in many species of Monticuli- 

 pora and in Constellaria ; but I have been unable to satisfy 

 myself as to the true cause of this phenomenon. In the outer 

 portion of the course of the corallites, when they have turned 

 out towards the surface, their walls always become recognisably 

 thickened, and they often, though not always, lose their quad- 

 rangular form, and become pentagonal or hexagonal (fig. 36, 

 B and c). The thickening of the walls of the tubes, however, 

 does not go so far as to entirely obliterate the original dis- 

 tinctness of the corallites. On the contrary, the primitive 

 boundary lines between adjoining tubes can always be readily 

 made out (fig. 36, d) ; and along these lines the corallites 

 readily separate from one another. 



Not only are all the corallites of one kind, in the sense 

 that there are no " interstitial corallites" of any kind, but long 

 sections show that the tabulation of all the tubes is the same. 

 All, namely, possess a moderate number of strong and com- 

 plete tabulae, which are developed in the curved portion of the 

 tubes just below the surface. Many of the tabulae are slightly 

 curved, either convex or concave, and they often join with one 

 another ; but others are straight. 



Hoi'izou and Locality. — Cincinnati Group, Cincinnati, Ohio. 



Monticulipora (Monotrypa) clavacoidea, James. 



(i^'ig- 37-) 



Chcetetes davacoideus, James, Cat. Lower Sil. Foss., 1871. (Named but not 

 described.) 

 „ ,, James, Cat. Lower Sil. Foss., 1875, p. i. 



Spec. Char. — Corallum forming a crust, which is attached by 

 the whole of its base to foreign objects, and is composed of 

 corallites which are uniformly disposed at right angles to the 



