Mr. T. R. Jones on some species of Leperditia. 95 



and does not come within the typical group of Leperditia, and 

 should be removed to a subgenus at least. 



It should be remarked that L. marpnala, as represented by 

 figs. 11-14 (and M. Keyserling's figures), differs from L. BaU 

 thicaj and the other species above mentioned, in having the 

 greatest convexity on the anterior and inferior region of the 

 valve, rather than on the central portion. 



Fig. 15 represents a cast in sandstone ( x 2 diam.), from the 

 Tilestones (Dowuton sandstone) of Kington in Herefordshire, 

 of a Leperditia apparently belonging to the species under notice. 

 It is associated with casts of small Lingula. Another specimen, 

 consisting of a cast of the left valve, in the same sandstone, ex- 

 hibits similar characters. 



These individuals measure /^ inch in length, and ^ inch in 

 breadth; they are rather more angular anteriorly than figs. 11 & 

 12 ; they present only obscure traces of a marginal rim ; and 

 their dorsal edge is not quite straight, but very slightly raised at 

 the centre. Otherwise the general form is similar in the English 

 and Russian specimens. 



The anterior and central tubercles in the Kington specimens 

 are distinctly seen, and have the same relative position and pro- 

 portions as in the St. Petersburgh specimens. 



With all the slight differences observable, considering the in- 

 difi*erent state of the casts, 1 do not think that the Kington spe- 

 cimens can be referred to any other than the Russian species. 



This is the first noticed occurrence of Leperditia in British 

 rocks*. The specimens are in the Museum of Practical Geology ; 

 and I am indebted to Mr. Salter for having kindly drawn my 

 attention to them. 



7. Leperditia Solvensis, nov. sp. PI. VII. fig. 16. 



Length ^ inch; breadth J^ inch. 



The impression of the outside of a small valve (an artificial 

 cast of which is represented, magnified 2 diameters, by fig. 16) 

 on a fragment of Lower Silurian schist from South Wales has 

 been kindly communicated to me by Mr. Salter. It is from the 

 Llandeilo flags (lowest portion) of Upper Solva, Solva Harbour, 

 St. David^s ; and is now in the Museum of Practical Geology. 



The valve was slightly convex f, narrow oblong in shape, nar- 



* Count Keyserhng, in his remarks on the L. marginata of Petschora- 

 Land, expressed his astonishment that the Upper Silurian rocks of England 

 had not yet yielded this species ; as it has at last made its appearance, we 

 may hope that it will soon be represented by numerous specimens in the 

 cabinets of the indefatigable collectors in Siluria. 



t The degree of convexity of the valve cannot be exactly ascertained, as 



