10 



LEPT.ENA analoga. 



TAB. DCXV.-/g^. 2. 



Spec. Char. Nearly semicircular^ with the front 

 either straightish or concave, much depressed 

 near the beak ; both valves inflated towards the 

 front, their margins suddenly deflected ; lower 

 valve flat near the beak; surface ornamented with 

 diverging- striae and concentrically undulated ; 

 waves numerous ; hinge-line bent, its area very 

 narrow ; beak pointed, hardly projecting. 



Syn. Prod u eta analoga. Phillips, loc. cit. 215. PL 

 VII. f. 10. 



i HIS shell grows much larger than the L. depressa (Tab. 

 459) ; its valves are more similar, both being inflated to- 

 wards the front, and its outline more rounded ; otherwise 

 it strongly resembles it. The area between the valves is 

 very narrow. 



It is possible that it may be the L. rugosa of Dalman ; 

 but the specimens I have seen from Sweden are most like 

 Li. depressa, a shell which I believe never occurs above the 

 limestone of the Devonian system. Rather frequent in the 

 mountain limestone of the North of England and in Ireland. 



LEPT^NA distorta. 

 TAB. DCX\. —Jig. 3. 



Spec. Char. Irregularly orbicular, concentrically 

 waved, striated ; front generally concave, the 

 margin flattened ; hinge-line straight, its area 

 triangular ; beak prominent. 



A THICKER shell than L. analoga ; well distinguished by 

 its projecting beak, very convex valves, which are not com- 

 pressed near the beak, and its smaller size. 



I suspect this is P. depressa of Phillips, 215. PI. VIII. f. 

 15 ; but as he says he cannot distinguish his specimens from 

 P. depressa of the Dudley limestone, I have not ventured 

 to quote his name as a synonym. The specimens fig. a. are 

 from the Isle of Man, by favour of Mr. Gilbertson. The 

 middle figure shows the impressions attributed to the 

 ovaria ; similar ones are frequent in casts of other species 

 of this genus, especially L. analoga. Fig. 3 b. shows the area 

 of the hinge in both valves. It is probably from Scotland. 



It is important to distinguish the two last species from 

 L. depressa, which belongs to the rocks of the Silurian 

 system, and it may readily be done with a little practice. 



