448 Br. Wheelton Hind — British Carboniferous Goniatites. 



Pericyclus virgattis, de Koninck, has a lateral saddle and lateral 

 lobe, but the shape of saddles and lobes are quite distinct from the 

 genus under description. PI. XVI, Fig. 1, shows the specimen 

 after the body-chamber has been detached. 



Pericyclus divakicattjm, Hind, 1905. (PI. XVI, Figs. 2-6.) 

 ■Glyphioceras divaricatum. Hind, Proc, E. Irish Acad., vol. xxv, ser. B, No. 4, 



p. 144, pi. vi, fig. 6. 

 1 Pericyclus virgatus, Foord & Crick, Cat. Foss. Ceph. Brit. Mus. Nat. Hist., 

 pt. iii, p. 146. 



Since the publication of this species much fresh material has 

 .accrued from many localities. The suture-line has also been seen 

 and more perfect specimens examined. I now think it should be 

 more correctly placed in the genus Pericijclus, Mojsisovics. I sliowed 

 much of my material to the lute Mr. Crick, and he expressed agree- 

 ment with my conclusions. In manj^ of the fossil lists I have 

 published this species has been confused with G. leyrichianum. 

 As the species was erected on fragmentary specimens I think it 

 best to redescribe and refigure it in more detail. Its lowest known 

 occurrence is in the Posidonomtja becheri beds of the Pendleside 

 Series, but it goes up as high as the 3rd Grit Shales of the Millstone 

 Grit. 



Specific Characters. — Shell discoidal, compressed, nmbilicated, 

 attaining a diameter of 70 mm. Greatest thickness at umbilical 

 margin. Height of outer whorl, four-sevenths of the diameter of the 

 shell. Whorls seven or eight, inclusion in the inner whorls almost 

 nil but becoming in the outer three or four more and more complete. 

 Umbilicus deep, open in the young, becoming relatively more 

 narrow with the growth of the shell, its margin rounded, the 

 under surface bevelled. Whorl elliptical in section, deeply im- 

 pressed by the preceding one. Periphery narrow, convex, becoming 

 obscurely keeled centrally in fully grown shells. Very feebly 

 convex at the sides. Body-chamber occupies two-thirds of the last 

 whorl. Suture-line as shown in Fig. 6. 



Test ornamented with many flattened ribs which bifurcate about 

 lialf-way between the umbilicus and the periphery. The grooves 

 between the ribs, linear at first, become broader and equal, about 

 half the measurement of the ribs in breadth. The ribs arch 

 forward on the side, but on the periphery form a fairly deep sinus 

 with concavity towards the younger part of tlie shell. A specimen 

 from Cracoe Fells shows also spiral marking on the ribs. 



Dimensiotis. — Greatest diameter, 70 mm. ; width at umbilicus, 

 25 mm. 



Localities. — 'Pendleside Series: silica quarry, Congleton Edge, 

 Dinckley Hall River Eibble, Flashy, in watercourse between 

 Butterhaw and Shelterton, andS. of Shelterton, Horsebridge Clough, 

 near Hebden Bridge. Posidonomya lecheri beds : Poolvash, Isle of 

 Man. Millstone Grit Shales : Eccup, near Leeds. Ireland: Foynes 

 and Foynes Island ; Lisdoonvarna, in the Pendleside Series. 



Observatio7is. — The flat dichotomous ribs distinguish this species 

 from all other described forms of the genus. P. virgatus, 

 de Koninck, sp., has more rounded ribs, and these are not dichotomous. 



