LEPTjENA. 17 



12. Leptjena Moorei, Dav. Plate I, fig. 18. 



Lept^na Moorei, Dav. 1847. Annals and Mag. of Nat. Hist., pi. xviii, fig. 1 a. 



— — Dav. Bull. Soc. Geol. France, vol. vi, 2d Series, p. 270. 



— — D'Orb. Prodome, vol. i, p. 220, 1849. 



Diagnosis. Shell small, depressed, wider than long, ornamented by numerous fine 

 costse, scarcely visible without a lens ; larger valve slightly convex ; area double, as wide, 

 or rather wider, than the shell ; deltidium small, chiefly filled up by the median tooth of 

 smaller valve, which tooth is grooved by four furrows, offering a passage for the muscular 

 fibres of attachment passed outwards. Length \\ lines ; width 2 lines. 



The muscular impressions in the interior of both valves are strongly developed in 

 this species, and indicate that it did not attain larger dimensions than those above 

 assigned to it. ' 



This elegant little species was first discovered in the beds of the upper lias above the 

 marlstone, near Ilminster, by Mr. Moore, to whom it is dedicated. The following section, 

 forwarded by Mr. Moore, shows the position of the bed containing the Leptanas : — 



1. Tlubbly beds, 6 to 10 feet, with numerous Ammonites. 



2. Clay, 8 inches. 



3. Yellow limestone, 3 to 4 inches. 



4. Layers of clay, 18 inches, Leptana Pearcei. 



5. Leptaena bed, 1 inch : L. Moorei, L. Bouchardii, and L. liasiana. 



6. Marlstone, %\ inches. 



7. Greenish sand, 4 inches, containing numerous Belemnites. 



8. Marlstone. 



I do not understand the reason which has induced M. D'Orbigny to place these 

 Zeptanas, and other species found in the same beds, in the lower Lias (Senemurien, 

 Prodrome, p. 220), where none, to my knowledge, have been discovered according with 

 my printed description and stratigraphical position of the species, which has not been 

 noticed out of England as yet. 



Plate I, fig. 18, shows the exact size of an adult specimen of this species. 

 ,, fig. 18 a— e are enlarged. 



It is not a rare species in its bed, Mr. Moore having found more than one hundred 

 specimens ; but from its minuteness it is difficult and tedious to collect. 



13. Leptaena Pearcei, Dav. Plate I, fig. 19. 



Lept.ena Pearcei, Dav. 1847. Annals and Mag. of Nat. Hist., pi. 18, fig. 4. 



_ _ j)av. Bull. Soc. Geol. de France, vol. vi, 2 de Serie, p. 270, 1850. 



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



D 



