52 PROCEEDINGS OF THE ACADEMY OF [1886. 



considerable resemblance to sections of Glathrodictyon cellulosum, 

 whose structure is somewhat coafser, having only four or five 

 lamellae within the space of a line, and more conspicuously 

 inflected in order to form pillars. 



As a fourth aberrant form of Stromatoporoids, a single speci- 

 men found in the upper Cincinnati group of Ohio is described 

 by the authors, about which I am unable to give an opinion of 

 my own, as from the rather vague description I cannot say that 

 anything similar ever was under my observation. 



After these expositions, a classification of the different tj^pes 

 of Stromatoporoids is attempted, and seven generic cadres are 

 proposed, most of which had been sketched already iu the 

 previous chapters. 



These proposed genera are: (1) Stromatopora Goldfuss, com- 

 prising all those forms consisting of concentrically superim- 

 posed laminae, each lamina separated from the other by a 

 distinct interlaminar space, which is crossed by numerous ver- 

 tical pillars. In some of these forms are radial, subhorizontal 

 canals or surface grooves placed round minor centres, which, 

 according to my own experience, are present in almost every 

 form of Stromatopora at least, in rudimentary development. 

 In addition to these characters, large vertical canals intersecting 

 the laminated masses are described by the authors, which they 

 believe to be analogous to the oscula of sponges. I have to 

 reject this opinion as erroneous. 



(2). Caunopora Phillips. Type, Caunopora placenta. Repre- 

 sentative form of the authors' Stromatophora perforata. I need 

 not enter again into a discussion of the value of this generic 

 distinction, as I have previously proved that these forms do not 

 represent one organism, but are coral stems, parasitically invested 

 with various kinds of Stromatopora, which in the same localities 

 grew perfectly free of such enclosed stems, erroneously believed 

 to be parts of the organism. 



(3). Glathrodictyon Nicholson, likewise, has been sufficiently 

 taken into consideration. 



(4). Stylodictyon Nicholson, is represented by two species, St. 

 columnare and St. retiforme. Besides the general structure of 

 Stromatopora, as special character of this genus, it is asserted 

 that a s^^stem of vertical columns of dense calcareous tissue per- 

 vades the laminated skeleton. The concentric arrangement 



