442 Mr. G. C. Crick on some 



give the dimensions at two diameters (A-B, C-D) as nearly 

 as possible at right angles to each other : — 



A-B. C-D. 



Diameter of shell about 96 mm. (100) 74 mm. (100) 



Width of umbilicus (at suture 



of shell) 32-5 „ (33-8) 22 „ (297) 



Width of umbilicus (at its 



margin) 40 „ (41-6) 30 „ (40-5) 



Height of outer whorl about 33 „ (34'3) 31 „ (41 -8) 



Ditto above preceding whorl . . 20 „ (20'8) 20 „ (27-0) 



Thickness of outer whorl about 64 „ (66'6) 53 „ (7D6) 



The dimensions given by De Koninck are : — longitudinal 

 diameter 85 millim. ; transverse diameter 58 millim. ; diameter 

 of umbilicus 30 millim. ; median height of aperture 21 millim. 



Remarks. The only example of this species that I have 

 seen is De Koninck's type specimen, which is in the collection 

 of the Geological Survey of Ireland. It is there labelled 

 " Goniatites Wrightn" but this appears to be only a manu- 

 script name. There is, however, no doubt whatever about its 

 being the type specimen of De Koninck's " Goniatites pli- 

 catihs.^ The locality of the specimen is not recorded on the 

 tablet to which it is fixed ; but De Koninck says : — " Un 

 certain combre [sic] de specimens de cette espese out 6t6 

 recueillis dans le calcaire de Kilmacan." De Koninck's 

 figure is somewhat restored, the specimen being of a more 

 elliptical form. 



Affinities and Differences. The present species is clearly 

 allied to Per. subplicatilis, but that is a much less inflated 

 shell. From Per. Hauchecornei f Holzapfel*, it differs by 

 its coarser ornaments and its much more inflated whorls. 



Horizon and Locality. Carboniferous Limestone : Kilma- 

 can, Ireland {fide de Koninck). 



Pericyclus subplicatilis, sp. n. (Figs. 8, 9.) 



Sp. char. Shell discoidal, somewhat compressed, mode- 

 rately widely umbilicated ; greatest thickness almost close to 

 the margin of the umbilicus, about two fifths of the diameter of 

 the shell ; height of outer whorl about two fifths of the dia- 

 meter of the shell. "Whorls six or seven ; inclusion four fifths ; 

 umbilicus rather deep, with subangular margin, exposing the 

 edges of the inner whorls, about three tenths of the diameter 

 of the shell in width. Whorl semielliptical in cross-section, 



* " Die Cephalopoden-fiihrenden Kalke des unteren Carbon von 

 Erdbach-Breitscheid bei Herborn," Pal. Abhandl., Dames & Kavser, 

 Bd. v. Heft 1, 1889, p. 36, pi. ii. tigs. 8-11 (especially figs. 11 & 11 a). 



