LEPMNA. 19 



lowing the contour of the larger valve, so that little space remained between them for the 

 body of the animal. Cardinal margin about half the width of the shell. Length 2 lines • 

 breadth the same. 



"The general form of this Lept&na approaches that of Productus, It closely resembles 

 L. oblonga. {Pander?) It has the same convexity and smoothness, and the beak is similarly 

 truncated by an apicial opening : the area and perpendicular opening has also some analogy 

 to the Russian species, but differs in the contour of the larger valve, and the notch in the 

 front margin." {Bouchard.) 



Obs. The above description was published by M. Bouchard, in the ' Annals of 

 Natural History,' Oct. 1847, and I have thought it desirable to reproduce it here. At 

 that period this species had not been discovered in England ; Mr. Moore was so fortunate 

 as to find in my presence, a short time since, two fine specimens in the Leptama beds of 

 the upper Lias, in the neighbourhood of Ilminster : its foreign locality being Pic de Saint 

 Loup, near Montpellier (Herault). In the ' Prodrome/ page 220, M. D'Orbigny, besides 

 placing this species and L. Bouchardii in the lower Lias, which is a stratigraphical 

 mistake, states it not to be a Leptana. It is to be regretted that, with both perfect 

 figures of the exterior and interior, M. D'Orbigny did not assign its generic position ; but 

 both M. Bouchard and myself consider its place for the present to be best among the 

 Lcptanas, with which they have many similar characters. 



Plate I, fig. 21, natural size. 

 „ fig. 21a, enlarged. 



XVI. Leptvena Bouchardii, Dav. Plate I, fig. 22. 



Lept^na Bouchardii, Dav. 1847. Annals and Mag. of Nat. Hist., pi. 18, fig. 3. 

 — — Dav. 1850. Bull. Soc. Geol. de France, vol. vi, 2 de Serie, 



p. 270. 1850. 

 _ _ ? D'Orb. Prodrome, 1849, vol. i, p. 220. 



Diagnosis. Shell very small, almost ovular; surface smooth; large valve very convex, 

 smaller valve concave, leaving only a little space for the animal ; beak small, not much 

 recurved ; area double, and cardinal margin smaller than the greatest width of the shell ; 

 deltidium very large. Length \\ ; width about half a line. 



Obs. This species is readily distinguished from Leptana liasiana by its more elegant 

 form ; the small valve is more regularly concave, and the larger one more convex. When 

 describing this species in the ' Annals,' I had not perceived that the beak was truncated at 

 its extremity by a minute circular foramen, as in L. liasiana; but which numerous speci- 

 mens, sent to me by Mr. Moore, have amply confirmed. This species appears never to have 

 attained larger dimensions ; as the internal characters presented by the smaller valve are 

 those belonging to a full-grown shell. L. Bouchardii was found, by Mr. Moore, associated 

 with Zcptana JSloorei, in the Leptaena bed, previously described under that species. 



Plate I, fig. 22, natural size. 

 „ fig. 22a, b, c, enlarged. 



