PERICYCLUS LEESONI. L53 



suture-line must not be relied upon too much for diagnostic purposes, but rather 

 the ornamentation of the shell, and also the absence of a sinus, lateral or peripheral, 

 in tlio border of the aperture. If Holzapfel be correct this latter feature casts a 

 further doubt upon the generic position assigned to this species, which clearly has 

 a peripheral sinus. 



Locality. — County of Kildare (exact locality unrecorded). 



Peeictclus ? Leesonj, G. 0. Oriel', sp. Plate XLVI, figs. 6 a — c. 



1899. Prolecanites Leesoni, G. C. Crick. Aim. Mag. Nat. Hist., ser. 7, vol. iii, 



p. 451, figs. Ua,b. 



Description.— Shell discoid, compressed, umbilicated ; the greatest thickness at 

 the umbilical margin, about one-third of the diameter of the shell; height of the 

 outer whorl about four-ninths of the same. Number of whorls not ascertainable ; 

 inclusion nearly three-fourths ; umbilicus rather shallow, with steeply sloping sides 

 and subangular margin (on the cast), its width about two-sevenths of the diameter 

 of the shell. Whorl subsagittate in section, the width nearly three-fourths of the 

 height, indented to about two-sevenths of its height by the preceding whorl ; peri- 

 phery narrow, somewhat flattened, especially towards the aperture, obscurely 

 defined ; sides very slightly convex ; umbilical zone narrow, well defined, sloping 

 towards the centre of the umbilicus. Body-chamber probably occupying at least a 

 complete whorl ; aperture not seen. Test so much eroded as to leave on the sides 

 only obscure traces of ornamentation, but the indications are strongly in favour of 

 the shell having been transversely costated; remains of ribbing are obscurely visible 

 on the sides and more plainly upon the periphery where the test is preserved in 

 places, their direction here indicating a rather deep and narrow hyponomic sinus. 

 As far as can be judged the ribbing seems to have been only slightly curved upon 

 the sides. Two shallow constrictions are present upon the cast, one near the 

 commencement of the body-chamber, the other more posteriorly situated; their 

 direction conforms to that of the ribbing. 



Dimensions. 



Diameter of shell 



„ umbilicus (edge to edge) 



„ ,, (suture to suture} 



Height of outer whorl 



,, above preceding whorl . 



Thickness at umbilical margin . 



Dype specimen in 



nf' Science ami . 



(Geolofriral Sun 



tion, No. C 



the Museum 

 Let, Dublin 

 rey CoUec- 

 . 748). 





90 



mm. 





27 



55 





24 



55 





t0- 5 



,, 





28 



J? 





29-5 



„ 



