PBRIOYCLTJS CLANENSIS. 151 



diameter, 85 mm. ; transverse diameter, 58 mm. ; diameter of umbilicus, 30 mm. ; 

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

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

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

 this circumstance probably causing its identity to be afterwards overlooked, for it 

 has been labelled " Goniatites Wrightii" as if it were an undescribed species; this 

 name exists only on the tablet. 



Affinities. — This species has been mistaken for Pericyclus fasciculatus ( = P. 

 fu/rcatus), M'Coy, from 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 P. subjMcatilis, Crick. P.funatus, J. Sowerby, may be an 

 allied form, but it has more numerous whorls and is a more compressed shell than 

 /'. plicatilis ; the plications also are much coarser in the former species. Pericyclus 

 plicatilis differs, according to Mr. Crick, from /'. Hauchecornei, Holzapfel, 1 in its 

 coarser ornaments and much more inflated whorls. 



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

 de Koninck). 



Peeioyclus? Clanensis, G. 0. Oriel-. Plate XLI, figs. 1 a — c. 



1888. Pericyclus Clanensis, G. C. Crick. Ann. Mag. Nat. Hist., ser. 7, vol. iii, 



p. 437, fig. 4. 



Description. — Shell discoid, rather compressed, especially laterally, somewhat 

 narrowly umbilicated ; greatest thickness near the edge of the umbilical 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 heighl 

 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 umbilicus. Body-chamber slightly exceeding the last 

 whorl in length; aperture not present, but, 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 where alone they 



'"Die Cephalopoden-fiihrenden Kalke des unteren Carbon von Erdbach-Breitscheid bei 

 Eerborn." (' Pal. Abhandl., Dames mid Kayser'), Bd. v, Heft 1, 1889, p. 30, \>\. ii, figs. 8—11 

 (especially figs. 11, 11 a). 



