Hind — Notes on the Homot axial Equivalents^ i^c. 113 



GL YPHIO CERA TIBM. 



Glyphioceras (Beyrichoceras) reticulatum, Phillips. PI. vi., 

 figs. 2, 3, 4, 5, 6. 



Ohservations — This species varies very considerably in the size of 

 its umbilicus and its ornament according to age. In the young, the 

 umbilicus is very wide, the whorls showing little or no inclusion ; and 

 the ornament consists of transverse, broad, rounded ribs, separated by 

 a sulcus, stronger on each margin, but carried round the periphery. 

 Later on, the ribs on the periphery become obsolete, but remain on 

 the lateral area ; and the periphery becomes reticulate, and often there 

 is a deep median peripheral sinus. This condition is the Gastrioceras 

 cirmmplicatile of Foord. The umbilicus contracts ; and the lateral 

 ribs now become obsolete, the whole shell being ornamented by close 

 fine reticulations. Still later, below the margin of the periphery, 

 the transverse strias become strongly arched forwards ; and the 

 umbilicus in full-grown examples becomes smaller, and its marginal 

 lines elevated. The aperture of the adult shell is sinuous, concave 

 at the periphery; a broad, tongue-like projection on each side below 

 the peripheral margin,' below which the aperture curves backwards, 

 and then forwards to end at the umbilical margin. Early characters 

 may persist in some specimens ; and hence the variety of form and 

 ornament of the shell, and the size of the umbilicus. It is not 

 surprising that the synonymy of this species is extensive. 



Localities — England : The Pendleside series. Ireland : Foynes 

 Island ; Cliffs of Moher, near Fishergate ; Coor spa well, near Ennis, 

 = Horizon of Pendleside series. Puffing Hole, Kilkce ; Cliffs of Moher 

 below O'Brien's Tower, = Horizon of Millstone Grits. 



Glyphioceras (Beyrichoceras) Davisi, Foord and Crick, 1897. 

 PI. vi., fig. 7. 



Glyphioceras Bavisi, Foord and Crick, 1897. Cat. Foss. Ceph. 

 Brit. Mus., p. 198, pi. iii., fig. 95. 



This shell is easily distinguished from all others by its acute 

 angular peiiphery and its undulating sides, and the elevated angular 

 margin to its umbilicus. The test is thin and crenulato- striate. The 

 acute margin is an adult character, and is not so well seen in young 

 examples. 



Localities — England : Above the Hardbed Coal, Halifax. Ireland : 

 Foynes Island ; Coor spa well, near Ennis, = Horizon of Pendleside 

 series ; Puffing Hole, Kilkee, = Horizon of Millstone Grits. 



