1886.] NATURAL SCIENCES OF PHILADELPHIA. 43 



furrows converging to certain centres can be discovered in almost 

 every form of Stromatopora if we examine a sufficient number of 

 well-preserved specimens. Certain forms show them always most 

 beautifully, particularl}^ those in which the tissue of the lamellae 

 and tlie i)illars has an open porous texture, which increases their 

 bulk, and diminishes the size of the interstitial spaces propor- 

 tionately. These forms have been pointed out by Winchell under 

 the generic name of Goenostroma, which distinction is not accepted 

 by Messrs. Nicholson and Murie, as the principal generic charac- 

 ter of Ccenostroma is said to be the occurrence of the radial 

 channel expansions which, being present in forms of ver}' different 

 affinitives, cannot, in their opinion, be used as a generic mark. 

 This is, in one way, true ; but if we consider that the forms com- 

 prehended under Ccenostroma are distinguished not only by their 

 radiated surface, but by the before-mentioned bulkiness of their 

 lamina; and pillai'S, and the minuteness of the interlaminar cavi- 

 ties, from the ordinary typical forms of Stromatopora, which have 

 compact, well-defined laminte and pillars, I think these two 

 characters combined allow a subdivision of Stromatopora into 

 two groups, which at the first glance are distinguishable by even 

 an inexperienced observer, although, as I admit, numerous tran- 

 sitory grades from one group to the other exist, which make it 

 difficult to draw a line of demarkation between them. 



The characters by which Prof. Nicholson distinguishes Stylo- 

 diclyon from Stromatopora most assuredly stand on a weaker basis 

 than those of Winchell's Ccenostrovia, as I will demonstrate here- 

 after when Messrs. Nicholson and Muvie's newly created genera 

 are reviewed. 



After having described these radiating horizontally expanded 

 channels, the authors give a description of certain so-called 

 vertical water canals, observed in many different forms of Stro- 

 matopora. 



There are two essentially difl["erent kinds of such canals verti- 

 cally traversing the laminated masses, and considered by the 

 authors as parts of the organism. In one of the cases we find 

 the mass of the Stromatopora perforated by comparatively large, 

 generally round, but sometimes elliptical canals, which have no 

 walls for themselves, and are evidently perforations by boring 

 animals. The nature of the channels and their totally irregular 

 distribution in the masses, proves this in a large number of spe- 

 cimens examined by me. 



