124 Prof. H. A. Nicholson’s Contributions 
opposite each other. The corallites often touch at points, but 
they are mostly separated by narrow interspaces occupied by 
a single row of large, angular, imperfectly walled interstitial 
tubes. Asscen in long sections (fig. 1, B) the ordinary coral- 
lites are crossed by a few remote and complete tabule, and 
the interstitial tubes are provided with numerous horizontal 
tabule, which at times anastomose and become subvesicular. 
Fig. 1. 
A 
Callopora ? glans, Nich. A, tangential section, enlarged twenty times ; 
B, longitudinal section, similarly enlarged. 
I am indebted for specimens of this curious species to the 
kindness of Mr. Madeley, of Dudley. It is of interest as 
forming in some respects a transition between the proper 
Fistulipore and the typical species of Callopora. This is 
shown both in the infolding of the walls of the corallites, 
which is such a characteristic feature of the species, and also 
in the fact that the walls of the interstitial tubes are so im- 
perfect as commonly to allow of a confluence of their tabule, 
giving rise to a partially vesicular interstitial tissue. Callo- 
pora? glans has some resemblances to one of the numerous 
Russian Monticuliporoids which have the general form of 
Monticulipora petropolitana; but I know of no form with 
which it could be confounded. 
Formation and Locality. Lower Ludlow shales, Sedgeley. 
6. Monotrypa crenulata, Nich. (Fig. 2.) 
The corallum in this species is hemispherical or subglobu- 
