>g6 



ZOANTHARIA. 



" alar septa," the tabulate area in the floor of the calice thus assuming the 

 form of a half-moon. Lastly, in the Devonian genus Anisophyllum 

 (fig. 175), the cardinal and alar septa are specially developed, and 



form three prominent ridges in the cup 

 of the calice. 



Outside of the typical family of the 

 Zaphre?itidce are various Zaphrentoid 

 corals which in the present state of our 

 knowledge can only provisionally be ar- 

 ranged in groups, and the true affinities 

 of which are not always clear. One 

 group of forms, which may be provision- 

 ally spoken of as that of the Hadrofthyl- 

 lid<z, comprises certain singular little 

 discoid corals for which the genera 

 Hadrophyllum, Baryphyllum, Coinbo- 

 fihyllum, and Microcyclus (fig. 176) have 

 been founded. In these singular types 

 the simple corallum has the form of a 

 flattened disc, the calice being so shallow as hardly to deserve the name, 

 while the base is also often flat, the corallum thus becoming coin-shaped. 

 There is generally a marked septal fossula, and the symmetry is con- 

 spicuously bilateral. The septa are smooth-edged, and irregular in 



Fig. 175. — a, Anisophyllum Agas- 

 sizi, slightly enlarged ; b, Calice of the 

 same, viewed from above — Devonian. 

 (After Milne-Edwards and Haime.) 



Fig. 176. — Microcyclus discus, from the Devonian (Hamilton Group) ot North America, a, 

 Upper surface of the corallum ; b, Under surface of the same. The cross shows the natural size 

 of the corallum. (Original.) 



length, and the interseptal loculi are filled up with stereoplasma, no 

 dissepiments nor tabulae being developed. All the types of this group, 

 so far as is certainly known, are found in rocks of Devonian age. 



The type of a second group {Palceocyclidce) is constituted by the 

 singular Palceocyclus porpita (fig. 177) of the Silurian rocks of Gotland. 1 

 The corallum in this form is discoidal, the flat circular base being covered 

 with a concentrically striated basal plate. The septa are forty-four, or 

 rarely forty, in number, alternately long and short, the " cardinal septum " 

 being shorter than the other septa, and being placed in a well-marked 

 "fossula" (figs. 158, and 177, a), the symmetry thus becoming bilateral. 

 The " counter septum " is not specially developed. All the septa are 

 tuberculated and have crenulated edges. There are no dissepiments nor 

 tabulae, but the interseptal loculi are not filled up with stereoplasma. In 

 this respect, as also in the crenulated form and more regular develop- 



1 Palceocyclus porpita certainly occurs also in the Wenlock Limestone of 

 Britain (Dudley), but the P. Fletcheri of the same formation does not appear to 

 be properly referable to the genus Palceocyclus, but belongs to Pholidophyllum. 



