206 R. B. Newton — On the Genus Leveillia. 



series in the Geological Department of the British Museum (Natural 

 History). The presence of the dorsal groove in these specimens, 

 evidently overlooked by Phillips, together with the well-developed 

 nodules bordering the umbilical margin, its highly ornamented 

 surface and quadrangular-shaped mouth, leave no doubt as to its 

 identification with this species. 



Formation and Locality. — Carboniferous Limestone of Bolland. 

 [Gilbertson Collection, British Museum.] 



Leveillia latidoksata (sp. nov.). PI. VL 



Specific characters. — Shell large, discoidal, biconcave, last whorl 

 massive and broad ; umbilicus wide, deep, with prominent angular- 

 shaped nodules, forming strong marginal serrations; nodules decrease 

 in size towards the younger volutions of the whorls ; the ventral 

 surface of last whorl is deep, oblique and furnished with numerous 

 transverse and closely set lines minutely beaded in structure, 

 similar lines cross these concentrically on the younger whorls ; 

 dorsal region moderately convex and very broad near the aperture, 

 but gradually diminishing in width towards the nucleus, ornamented 

 with strong and broad ribs, which are crossed transversely by fine 

 closely-set stride; ribs with a slightly wavy contour and widest near 

 the umbilical margins, decreasing in width and becoming straighter 

 and more numerous as they approach each side of the median 

 groove ; aperture quadrangular ; groove narrow and prominent ; 

 shell structure thick and robust. 



Observations. — This species is distinguished from all others by its 

 large size, a lesser convexity, and greater width of the dorsal region, 

 together with the presence of the broad and prominent ribs over 

 the back instead of the spirally beaded surface. The important 

 angular-shaped nodules, with the deep cavity between each, gives 

 rise to a strongly serrated appearance, especially when the shell is 

 viewed dorsally. Another peculiarity, only shared by one other 

 species, viz. L. Duponti, De Koninck, is the fact that these nodules 

 follow the dorsal plane of convexity and extend down the ventral 

 surface only, without forming ridges by being produced over the 

 back as is general in the nodulated species of the genus. The 

 exception mentioned, though possessing this character, has a very 

 differently shaped aperture, and its surface ornament presents the 

 usual spirally beaded structure. 



There are three specimens of our species in the British Museum, 

 one of which has been sectioned to show the growth and contiguity 

 of the whorls as well as to prove the monothalamous nature of the 

 genus. 



Formation and Locality. — Carboniferous Limestone, Dublin and 

 Eildare. British Museum (Natural History). 



