PLATE XX. 



Fig. 

 1 Edmondia sulcata, Phillips. Left aspect (natural size) of a cast. Carboniferous 



Limestone, Redesdale, Northumberland. 

 2. — — The same specimen with the umbone removed (by the dark 



line on the latter figure), showing the left cartilage 



muscular fulcrum {a). 

 ,3. — — The left cartilage muscular fulcrum enlarged. 



4. — — Both cartilage muscular fulcra (enlarged), as seen on the 



specimen at fig. 2, when looking on its dorsal 

 aspect. 



5. Allerisma sulcata, Fleming. Left aspect (natural size) of a cast, showing impres- 



sions of the anterior and posterior adductor muscles 

 {a, b) ; sinus in the pallial line (c) ; and pimples 

 radiating over the posterior half of the shell. Car- 

 boniferous Shale, Redesdale, Northumberland. 



6. Leptsena analago, /. de C. Sowerhy. Foraminiferous valve, twice the natural size : 



testiferous. a, teeth ; 3, saucer-shaped muscular ful- 

 crum ; c, ventral median plate ; d, fissure ; e, foramen ; 

 /, (?) cardinal muscular impressions \ g, (?) valvular 

 muscular ditto ; h, superior pedicle muscular ditto ; 

 i, primary trunks of vascular system ; j, area. Car- 

 boniferous Shale, Redesdale, Northumberland. 



(The letter d referring to the fissure — that is, the triangular 

 opening between tue teeth a — has been inadvertently omitted.) 



7. — — Imperforate valve, a, dental sockets ; b, dorsal median 



plate ; c, impressions of the anterior divisions of the 

 valvular muscles ; d, ditto of the posterior divisions ; 

 e, cardinal muscular fulcrum (divided) ; /, primary 

 trunks of the vascular system passing out from 

 between the divisions of the adductor muscular im- 

 pressions ; g, area. Same locality as last. 

 (The reference letter, h, is cancelled.) 



8. Anomia ephippium, Linnceus. Upper valve, rather enlarged, to show the dendritic 



character of the impression of the stopper muscle {a). 



9. Criopus turbinatus, Po/e. Attached valve (enlarged), showing the digitated genito- 



vascular impressions (in relief), a. 



