16 BKITISH OOLITIC AND LIASIC BRACHIOPODA. 



gona, papillata, hieroglyphica, recurvirostris, digitata, antiqua, &c. This last-named species 

 approaching more than any I know to our Th. rustica, and in all good genera we ought to 

 find a graduated scale from the simple to the compound. Thecidea rustica was discovered 

 by Mr. Moore in the upper lias, in the same bed containing Lept. Moorei, Bouchardii, 

 Liasiana, Beared, Sp. Ilminsteriensis, &c, and therefore higher up than Tit. Moorei and 

 Bouchardii. Mr, Moore has given it the name of Th. rustica, which I readily adopt ; it is 

 much to be regretted that hitherto only the smaller valve has been found; it does not 

 appear very rare in its bed, if one inclines to take the trouble of seeking it, which can be 

 done only by washing the sandy clay bed where it is found, and then carefully picking them 

 out, after having extended small portions of the washed bed on a plate. In this manner, also, 

 are obtained the Leptanas, and numerous Foraminifera with which these beds abound ; 

 its locality is the neighbourhood of Ilminster. 



Plate I, fig. 14, natural size, from specimens belonging to Mr. Moore ; fig. 14, a, b, 

 enlarged exterior and interior. 



Genus — Lept^ena, Batman. 1827. 



Shell inequivalved, equilateral, generally transverse, sometimes oval, always compressed ; 

 smooth, striated, or exteriorly costated : larger valve, more or less convex or concave, some- 

 times bent or geniculated ; beak more or less produced, straight, sometimes recurved, and 

 perforated at its extremity by a very small circular opening ; separated from the cardinal 

 edge by a more or less elevated triangular or canaliculated area : smaller valve, concave or 

 convex, following the large valve in its different curves, beak of smaller valve not much 

 produced, with or without a linear area : deltideum complete, triangular, with angles more 

 or less open, without reference to the development of the area; often notched at its base for 

 the passage of the tendinous fibres of attachment ; hinge transverse, straight, linear ; teeth 

 differently disposed, but always provided with two principal diverging teeth on the larger 

 valve, which are received by sockets placed on each side of the central bifid or trifid tooth 

 of the smaller valve : no internal calcareous supports. 



Obs. We will not at present discuss the different opinions lately brought forward on this 

 genus, or its subdivisions, each author having his way of thinking on this subject, which 

 has involved us in great confusion ; the same shell is thus for some a Strophomena, for 

 others a Leptana, Leptagonia Chonetes, Broductus, &c. All we shall here state is, that 

 the genus was not known to occur above the Pala;ozoic series before 1847, at which time 

 M. Bouchard and myself described several species from the lower oolitic or liasic 

 deposits ; and we are now acquainted with the five following species : — Leptana Moorei, 

 L. Biercei, L. granulosa, L. liasiana and L. Bouchardii, all of which are found in 

 England. Lept. liasiana (Bouch.) alone having as yet been discovered on the Continent. 



