species of Paleozoic Bivalved Eniomostraca, 407 



ferous strata throughout the British Isles. The largest speci- 

 mens we have seen were found by Mr. C. Moore, F.G.S., in the 

 Mountain-Limestone at Weston-super-Mare, in Somerset. L, 

 Okeni never seems to have quite such sharp angles at the end 

 of the hinge-line as L. Balthica and other Silurian Lepei'ditia 

 have. 



2. Leperditia oblonguj n. sp. PL XX. fig. 5. 



Length -o\ inch, height 4^ inch. 



Among the specimens of L. Okeni with which M. Giimbel 

 favoured us are a few Entomostraca that do not belong to that 

 species. One of these is a small Leperditia, nearly oblong, with 

 rounded ends, nearly alike in contour, but one rather flatter than 

 the other ; the hinge-line long and straight ; the ventral line 

 gently and evenly curved ; surface smooth. 



Such small oblong Leperditia as this are rare, but are found 

 in the Carboniferous rocks, and form a passage from iy. Okeni 

 (which in its small varieties imitates the small Silurian Leper- 

 ditia : see Ann. Nat. Hist. ser. 3. vol. i. pi. 10) to L. Koninckiana, 

 nob. MS., of the Carboniferous Limestone of Belgium. 



3. Leperditia parallela, n. sp. PI. XX. figs. 6 a, 6 b. 



Length -^ inch, height -pi-Q- inch, thickness -j-^ inch. 

 This is a still smaller Leperditia, long, gibbous, and almost 

 cylindrical, with long straight hinge-line, coming forward almost 

 flush with the gently rounded anterior end, and retreating from 

 the obliquely rounded hinder end; ventral edge nearly straight, 

 sharply curving at its posterior end, and obliquely rising in 

 front. 



4. Leperditia suhorhiculata, Miinster, sp. PI. XX. 

 figs. 7 a-7 c. 



Cy there suborbiculata, Miinster, Jahrb. f. Min. 1830, p. 65, no. 16. 



Length -,V inch, height -^ inch. 



Excepting for convenience^ sake, and from the possibility of the 

 soft parts of the Entomostracan inhabitant of such a carapace 

 having some difiierence in its inner organs from those of the 

 ovate Leperditia, w^e could not venture to separate this shorter 

 and rounder form from L. Okeni ; and, after all, any diff'erences 

 the animal had may have been sexual only. Excepting in being 

 nearly orbicular (the ventral margin having a very bold curve, 

 and being only slightly oblique anteriorly), it does not appear 

 to difi'er from the more common form, with which it is asso- 

 ciated in Britain as in Bavaria. It has a moderate ventral over- 

 lap, and has the dorsal hump on the left valve. Probably it 

 ought to be regarded as L, Okeni, var. suborbiculata, Miinster. 



