438 Mr. G. C. Crick on some 



sinus ; the outer whoil witli 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'o „ (28'5) 



Hei-ht of outer whorl 49 „ (417) 



Ditto above preceding whorl 32 „ (27'2) 



Thicknes.s of outer whorl about 44 „ (37'4) 



RetnarJcs. The example on which the present species is 

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

 been labelled Goniaiites Brownii, M'Coj *, 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 

 desciiption, I have entirely disregarded the name it bears. 

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

 Fei'. clanensis is suggested for it. 



Affinities and Differences. Compared with Pericydus rotu- 

 h'jor7nis'\ and al.so Per. Bailyi t\\\s species has more inflated 

 whorls and a much narrower umbilicus. 



Horizon and Locality. Carboniferous Limestone : Clane, 

 Co. Kildare, Ireland. 



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



Sjy. 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, subglubose, sides 

 tiatteiR'd ; umbilicus large, acute-edged, exceeding one tliird the diameter 

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

 acute ; tir^t lateral lobe slightly exceeding the dorsal iu length, very wide, 

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

 second lateral lube very wide, obtusely rounded. 



"From the U. striutus, Sow., which the species most resembles, it is , 

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

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

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

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

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



t See svpnt, p. 434. 



