438 Mr. G. C. Crick on some 



sinus ; the outer whorl with a few slight constrictions parallel 

 to the lines of growth. 



Dimensions. 



Diameter of shell 117-5 mm. (100) 



Width of umbilicus (at suture of shell) 31 „ (26-3) 



Width of umbilicus (at its margin) . . 33'5 „ (28'5) 



Height of outer whorl 49 „ (417) 



Ditto above preceding whorl 32 „ (27'2) 



Thickness of outer whorl about 44 ,, (37 - 4) 



Remarks. The example on which the present species is 

 founded is in the Science and Art Museum, Dublin. It has 

 been labelled Goniatites Brownu, M'Coy * , and there is just 

 the possibility of its having been the type specimen. As it 

 does not, however, agree either with M' Coy's figure or his 

 description, I have entirely disregarded the name it bears. 

 Since the example is from Clane, Co. Kildare, the name 

 Per. clanensis is suggested for it. 



Affinities and Differences. Compared with Pericyclus rotu- 

 lijormis j" and also Per. Bailyi this species has more inflated 

 whorls and a much narrower umbilicus. 



Horizon and Locality. Carboniferous Limestone : Clane, 

 Co. Kildare, Ireland. 



Pericyclus Bailyi, sp. n. (Figs. 6, 7.) 



Sj). char. Shell discoidal, somewhat compressed, rather 

 widely umbilicated ; greatest thickness almost close to the 

 umbilical margin, about four ninths of the diameter of the 

 shell ; height of outer whorl about three sevenths of the 

 shell. Whorls about seven in number ; inclusion three 

 fourths; umbilicus deep, with subangular margin, nearly 

 one third of the diameter of the shell in width. Whorl 



* F. M'Coy, Synopsis Carb. Foss. Ireland, p. 12, pi. iv. fig 17. M'Coy's 

 description of this species is as follows : — " Discoid, subglobose, sides 

 flattened ; umbilicus large, acute-edged, exceeding one third the diameter 

 of the shell ; surface smooth ; septa, dorsal lobe small, bitid ; dorsal sinus 

 acute ; first lateral lobe slightly exceeding the dorsal in length, very wide, 

 rounded ; lateral sinus twice as long as the dorsal, acute, linguiform ; 

 second lateral lobe very wide, obtusely rounded. 



"From the G. striatus, Sow., which the species most resembles, it is 

 distinguished internally by its much shorter and wider first lateral lobe ; 

 the tame character distinguishes it from the G. sphcericus, Sow., and 

 from both it is distinguished externally by its smooth surface, and from 

 all the species of the same form by the large size of the umbilicus. 

 Diameter 2 inches 2 lines, thickness 1 inch 1 line." 



f See supra, p. 434. 



