GENERA OF CH^ETETID^E AND MONTICULIPORID^E. 323 



Monticulipora (Monotrypa) Winter!, Nich. 

 (PI. XIIL, figs. 5; 5 a; PI. XIV., figs. 2, 2 a.) 



Spec. Char. Corallum when young, discoid and concavo- 

 convex ; when adult, hemispherical or subglobular. Young 

 examples may be three or four lines in diameter, and less than 

 two lines in greatest height ; while fully-grown specimens may 

 be more than an inch and a half in diameter, and more than an 

 inch in height. The base is free, or attached to some foreign 

 body at one point, and it is either flat or concave, and is 

 covered by a concentrically-striated epithecal membrane. The 

 corallites radiate from the base and open upon the upper sur- 

 face by thin -walled polygonal calices. The surface shows 

 clusters of slightly extra-sized corallites, which are only occa- 

 sionally elevated to form low " monticules." The corallites 

 are all uniformly thin-walled, strictly angular or prismatic in 

 form, and subequal in size, averaging a quarter of a line in 

 diameter. In internal structure they are all alike, all being 

 provided with delicate, remote, complete, and horizontal 

 tabulae. 



Obs. Examples of this species are of common occurrence in 

 the Devonian Limestone of Gerolstein, and are so entirely 

 similar in form (PI. XIIL, figs. 5, 5 a) to the Lower Silurian 

 M. petropolitana, Pand., that a merely macroscopic examina- 

 tion would almost certainly have led to their being identified 

 with the latter form. A microscopic examination, however, 

 shows that their structure is that of Monotrypa, and not that 

 of Diplotrypa, all the tubes alike being essentially similar in 

 their internal characters. Tangential sections (PI. XIV., fig. 2) 

 show that the tubes are essentially uniform in size, a few 

 slightly larger ones forming scattered clusters, while such in- 

 tercalated small ones as are present are obviously merely young 

 corallites. All the tubes also are bounded by very delicate 

 walls, and are regular, angular, and prismatic. Vertical sec- 

 tions (PI. XIV., fig. 2 a] show a complete identity in structure 



