7iew or little-known Goniatites /rom Ireland. 441 



Affinities and Differences. The present species issom'^\r}iat 

 more inflated and more widely nmbilicated than Periri/clnx 

 clanensis * ; it is also more inflated than PericjjcJus roltdi- 

 formis\^ and lacks the con.strictions characteristic of that 

 species. 



Horizon and Locality. All the examples of this species 

 that 1 have seen are from St. Doiilagh's, Co. Dublin, 

 Ireland. Three of these are in Dr. Foord's collectio-i, and 

 one (the largest) is in the British Museum collection 

 (no. C. 29S). 



Pericyclns plicatilis, L. G. de Koninck, sp. 



Goniatifes pUcatilis, L. G. de Koiiinck, "Sur qiiplques C^phalopodes 

 uouveaux dii Calcaire carbonilere de I'lrlande," Ann. Soc. g(5ol. de 

 Belg. vol. ix., .M(5moires, p. -oo, pi. v. figs. .3 & 4 (erroneously stated 

 to be pi. vi. tigs. 3 .t 4 (1881)). 



Sp. char. Shell subglobose, rather widely umbilicated ; 

 greatest thickness at the umbilical margin, about two thirds 

 of the diameter of the shell ; height of outer whorl about 

 two fifths of the diameter of the shell. Whorls (? number) ; 

 inclusion five sixths ; umbilicus deep, with angular maro-in 

 and steep sides, about one third of the diameter of the shell 

 in width, exposing the angular edges of the inner whorls. 

 Whorl semilunate in cross-section, much wider than hi^-h • 

 indented to about two thirds of its height by the precedino- 

 whorl ; periphery broadly convex, imperfectly defined, con- 

 tinuous with the sides; sides feebly convex; umbilical zone 

 well defined, fairly wide, nearly perpendicular to the plane of 

 symmetry of the shell, but slo|)ing a little towards the centre 

 of the umbilicus. Body-chamber apparently occupvin<>- 

 nearly the whole of the last whorl ; aperture not seen, but 

 (judging by the direction of the growth-lines) the peristome 

 probably nearly straight on the lateral area, and with a very 

 broad and fairly deep hyponomic sinus. Chambers (? depth) ; 

 suture-line only partially seen. Test ornamented with narrow 

 prominent riblets, which pass froni- the margin of the umbili- 

 cus in a nearly radial direction over about two thirds of the 

 lateral area, and then turn backward somewhat abruptly, 

 forming on the periphery a very broad and fairly deep hypo- 

 nomic sinus ; the interspaces are somewhat wider than the 

 riblets ; the whole suriace with very fine growth-lines parallel 

 to the riblets. 



Diintnsions. Owing to the distortion of the specimen I 



♦ See stijira, p. 436. f See siqva, p. 434. 



