u 



Wirrialpa specimens would seem to correspond well in diameter 

 with the sectional figures of Coscinocyathus given by Dr. Borne- 

 mann. 



Genus Etiimophyllu.m. 



The specimens referred to this genus are small or of medium 

 size, with a diameter of from a quarter to three quarters of an 

 inch. The general form of our fossils is that of a long, slowly 

 tapering, inverted cone, at times becoming turbinate, or rather 

 cup-shaped, and circular or oval in section, with a large central 

 tubular, or occasionally infundibuliform cavity. When the sub- 

 stance of the corals has weathered more rapidly than the infilling 

 matrix, the latter is left projecting as a plug, giving to them a 

 defined and characteristic appearance. The line of demarcation 

 between this plug and the narrow external ring formed by the 

 septa is a very marked one. In one of Prof. Tate's specimens 

 the conate outline of the calice is clearly indicated by the plug of 

 limestone infilling it. In weathered specimens free of matrix, the 

 outer edges of the septa are usually visible as vertical lamellae, 

 when the resemblance to an ordinary decorticated Rugose coral 

 is very strong. The outer covering, answering to the epitheca, 

 has not been observed, but certain peculiar appearances here 

 visible will be referred to later. Observation has not shown this 

 to be other than a free form. 



The minute anatomy resembles both that of Archceocyathus and 

 Ethmophyllum, in possessing a well-marked septal area, always 

 apparent in a transverse section (PI. II., figs. 1-3) defined by an 

 outer and inner lamina, bounding the outside and inside of the 

 funnel-shaped corallum. 



The septa in all our specimens are stout, rigid, and well marked 

 lamellae extending from the top to the bottom of the corallum, 

 possessing, w4ien viewed transversely, a general pillar-like ap- 

 pearance, and increasing by the interpolation of new septa, 

 through the subdivision, or bifurcation of the older. The outer 

 and inner ends of the septa in many instances are seen to ex- 

 pand more or less, where disrupted from the bounding laminae, 

 and w^hen in this condition are not unlike the pillars of Recepta- 

 culites (PL II., fig. 4). _ 



In Archceocyatlms dissepiments are profusely developed, divid- 

 ing the interseptal spaces into loculi, a character which is excel- 

 lently shown in one of Dr. Hinde's figures. In BthmophyUiwi, 

 however, this dissepimental tissue is said to be apparently want- 

 ing, and the vast majority of the specimens before me agree with 

 Ethmophyllum in this peculiarity (PL II., figs. 1 and 3). At the 

 same time one section (PL II., fig 2) does exhibit simple, straight, 

 transverse bars between the septa more or less in a line, dividing 

 the loculi into rhomboidal spaces. These dissepiments, for such 



