254 Mr. H. J. Carter on the 



Stromatopora, Goldfuss. 



Gen. char. Corallum concentrically laminar, massive, in- 

 crusting ; curve of the lamina large, simple, and expanded, 

 or small, short, and abruptly undulating, following one or 

 several axes, directed in the same or several ways in accor- 

 dance with the number and direction of the undulations, com- 

 posed of coenenchyma formed of rectilinear or curvilinear fibre, 

 and presenting in the course of the lamina isolated spots of 

 stellate venation, whose flexuous rays, becoming divided and 

 subdivided into branches, finally terminate by anastomosing 

 with those of the neighbouring stellations and ccenosarcal 

 cavities respectively (PI. XV. fig. 1). 



Lamtnce. — Variable in thickness according to the fineness or 

 coarseness of the specimen or species ; in some not more 

 than l-144th inch, in others wider ; but this measurement 

 must not be confounded with the coarse yet characteristic 

 lamination of " weathering " in the mass, where a variable 

 number of the thin laminae may be left together; again 

 varying in the undulating structure, which frequently resem- 

 bles the "gnarly grain" of an oak panel, in contradistinction 

 to the less wavy condition of the layer in the " straighter 

 grain," well illustrated in the horizontal section of a tree, 

 where the same lines are sometimes close together and some- 

 times wide apart in the same concentricity. 



Rectilinear and Curvilinear Structure of the Coenenchyma. — 

 Baron Rosen in his ' Thesis,' to which I have before alluded, 

 clearly describes and illustrates these two structures (' Ueber 

 die Natur der Strom atoporen,' 1867, pp. 6, 7, and tabb. 1, 6) 

 in his S. typica and 8. Schmidtii respectively, which in a 

 general way holds good throughout, but, of course, is subject 

 to modifications which more particularly belong to the descrip- 

 tions of the species respectively. 



Considering the " rectilinear structure " first (PI. XV. 

 fig. 2), this may be divided into a horizontal and a vertical 

 facies — in which the former presents a number of triangular or 

 polygonal (fig. 2, a) , and the latter a number of rectangular 

 spaces (fig. 3, dd). In the horizontal section (fig. 2) the 

 triangular spaces are formed by the extension of straight lines 

 between a number of more decided puncta (fig. 2, d d) } 

 which are the truncated ends of the vertical lines or rods that 

 form the most striking part of the rectangular structure in the 

 vertical section (fig. 3, a a). Thus, as this structure is 

 repeated in each lamina, the triangular spaces appear on the 

 upper and under side of it respectively, while the interval, 

 now filled with transparent calcitc (fig. 2, e e, and fig. 3, dd), 



