SUPPLEMENT. 489 



umbilical furrow, Number of whorls five to six. These are very tumid and 

 separated by a deeply impressed, almost canaliculate suture ; sutural angle very 

 oblique. No ornamentation, other than growth-lines, which are rugose and 

 varix-like on the body- whorl. Aperture nearly circular with thin sharp lips. 



Relations and Distribution. — This species resembles in some respect Paludina 

 scotica, which occurs in the Hebrides on approximately the same horizon. It also 

 differs but little from Paludina vivipara, being perhaps of smaller habit and with 

 a more sloping sutural angle and more convex whorls than the existing species. 

 On the other hand the Paludinas of the Upper Purbeck are for the most part 

 very different. 



Paludina Langtonensis is abundant in the so-called Paludina-hed, a kind of 

 mortar-like deposit which occurs high up in the Chipping Norton limestone at 

 Langton Bridge, along with other freshwater species and occasionally seeds of 

 Chara, &c. But associated with these are species of Ceritlmim and Nerinpea along 

 with a small variety of Amheiieya nodosa — apparently a Bathonian fauna. This 

 deposit, where developed, is found to underlie a gritty bed containing teeth and 

 palates of fish. 



Paludina Langtonensis also occurs in great abundance at Castle Barn, three and 

 a half miles from Chipping Norton, and traces may likewise be seen at Sharp's 

 Hill in a similar position. 



Genus — Valvata, Milller, 1774i. 



Shell umbilicated, turbinoid, or subdiscoidal, spire but slightly prominent, whorls 

 convex and feiu ; aperture circular, oblique ; peristome entire, thin, sharp, slightly 

 expanded. 



449. Valvata comes, sp. nov. Plate XLIII, fig. 27 ; and Plate XLIV, figs. 2 a, 2 b. 



The transverse diameter of these little shells does not exceed 3 mm. Judging 

 from the figure they diflPer slightly from Valvata praecursor, Tate (' Quart. Journ. 

 Geol. Soc,' vol. xxix, p. 348, pi. xii, fig. 9). The spire is more salient than in 

 Valvata cristata. 



Somewhat rare in the Paludina-hed at Lan<>'ton Bridsre. 



