PERTCYCLFS CLANENSTR. 151 



diameter, 85 mm. ; transverse diameter, 58 mm. ; diameter of umbilicus, :}0 mm. ; 

 median height of the aperture, 21 mm. These agree very closely with the measure- 

 ments given aljovo, though the specimen appears to have been fractured a little 

 after it had left de Koninck's hands. His drawing represents it as undistorted, 

 this circumstance prol)al)ly causing its identity to l)e afterwards overlooked, for it 

 has l)een labelled " (itniintitcs Wrhjliiii" as if it were an undescril)ed species; this 

 name exists onl}' on the tablet. 



Ajfiiiities. — This species has been mistaken for Peril- ijdnx faxrinihifiis ( = P. 

 furcatiif:), M'Coy, fi-om which it is easily distinguished by the larger number and less 

 prominent character of its ribs, and the absence of bifurcation in them. It is also 

 a much more inflated shell ; this character, together with its deep umbilicus, dis- 

 tinguishes it also from /\ siiJijilirKfUis, Crick. P. fimafns, J. Sowerby, may be an 

 allied form, l)ut it has luoi-e numerous whorls and is a more compressed shell than 

 P. p}i<-(ifilis ; the plications also are much coarser in the former species. Periryrhis 

 plii-dfilis diffei-s, according to Mr. Crick, from /'. ILiiiHifconwi, Holzapfel,' in its 

 coarser ornaments and much more inflated wdiorls. 



LocaUti/. — Kilmacat, county of Limerick (erroneously written " Kilmacan " by 

 de Koninck). 



PEinovcLus? Clanensis, G. C. ('rid-. Plate XLI, figs. 1 a — r. 



1888. Pericyclus Clanensis, G. C. Crick. Auu. Mag. Nat. Hist., scr. 7, vol. iii, 



p. 437, fig. 4. 



Dosrriptkm. — Sliell discoid, I'ather compressed, especially laterally, somewhat 

 narrowly iimbilicated ; greatest thickness near the edge of the uinl)ilical margin, 

 rather more than four-elevenths of the diameter of the shell. Whorls few ; their 

 number not ascertainable in the only specimen at present known ; inclusion nearly 

 two-thirds ; umbilicus shallow, rather more than one-fourth of the diameter of the 

 shell in width, with narrowly rounded margin. Whorl semi-elliptical in cross-section, 

 somewhat higher than wide ; indented to rather more than one-third of its height 

 by the preceding whorl. Periphery convex, imperfectly defined ; sides slightly 

 convex, somewhat flattened near the umbilicus ; umbilical zone extremely narrow, 

 sloping a little towards the nm])ilicus. Body-chamber slightly exceeding the last 

 whorl in length; aperture not present, ])ut, judging by the lines of growth, there 

 was probably a moderately prominent lateral crest and a broad and rather deep 

 hyponomic sinus. Chambers (near the base of the body-chamber wliere alone they 



'"Die Cephalopoilen-fiilironden Kalkc des unteren Carbon von Enlhacli-Breitsclieid l)ei 

 Horborn." (' Pal. Abhaudl., Dames nnd Kayser '), Bd. v. Heft 1, 1889, p. 3<i, pi. ii, figs. 8—11 

 (especially figs. 11, 11a). 



