Bivalves, 

 l'ictorum, 



Suborbicu- 

 laris, 



BiAentata, 



©emssata, 



Purpurea, 



FerruginO' 

 sa. 



Nitens. 



XXVII. 



88 



7. Piclorum. Shell sub-arcuated, olive green, con- 

 centrically wrinkled; beak near to one side; hinge 

 nearly straight, from which it declines alike to both ends; 

 a single broad crenated tooth, Avith two lateral laminae 

 in one valve, and one in the opposite, lock into each 

 other. Length one inch, breadth an inch and three 

 quarters. 



Brit. Shells, tab. 174. 



Found by Mr Montagu in the river Kennet, above 

 the town of Newbury, in Berkshire. 



Q. Suhorbicularis. Shell sub-pellucid, sub-orbicular, 

 faintly striated transversely ; margin opposite the hinge 

 nearly straight ; hinge central, with a single tooth im- 

 mediately under the beak, locking into a double one in 

 the opposite valve, with a laminated tooth behind the 

 beak in each, somewhat remote. Length three-eighths 

 of an inch, breadth half an inch. 

 Test. Brit, tab 26. fig. 6. 



Discovered by Mr Montagu in limestone at Plymouth, 

 and detached from any other substance in Salcomb Bay. 

 Mr Laskey found it at Dunbar, and we have found it 

 in the Murray Frith, and in Zetland. 



10. Bidentata: Shell sub-oval, thin, compressed, dir- 

 ty white ; beak small, placed near to one end, and a lit- 

 tle reclined; hinge with two broad erect laminated 

 teeth in one valve. Length one-eighth of an inch, ra- 

 ther more in breadth. 



Test. Brii. tab. 26. fig. 5. 

 Found by Mr Montagu in Salcomb Bay, Devonshire, 

 burrowed in old oyster shells. 



11. Bccumita. Shell ovate, white, with concentric 

 ridges, decussated by regular longitudinal striae, form- 

 ing tubercles at the anterior end; margin waved; beak 

 obtuse, recurved, and placed nearest to one end ; hinge 

 with a broad erect tooth in one valve, and a projecting 

 indented lamina on the other for its l-eception. Length 

 nearly half an inch, breadth rather more". 



Test. Brit. tab. 28. fig. 1. 

 Found near Dunbar, where it is rare. 



12. Purpurea. Shell ovate, slightly wrinkled trans- 

 versely, and of a purple colour about the beak, shaded 

 to a white towards the margin ; beak placed consider- 

 ably to one side, and turning towards the shorter end ; 

 hinge with a single erect tooth in each valve, slightly 

 bifid. Diameter about a line. 



Found by Mr Montagu amongst coralhne in deep wa- 

 ter on the coast of Devon ; very rare. 



13. Ferruginosa. Shell svibovate, moderately con- 

 vex, white, with obsolete wrinkles ; beak obtuse, pla- 

 ced nearest to one end ; front margin nearly straight ; 

 hinge furnished with two projecting teeth, one of which 

 is erect, the other turns inwards, and slopes downwards; 

 the teeth are separated by a large triangular notch. 

 Length about a quarter of an inch, breadth half an 

 inch. 



Test. Brit. tab. 26. fig. 2. 

 Found by Mr Laskey on the shore near Dunbar. It 

 is probably a native of Weymouth. 



14. Nitens. Shell ovate, of a pink colour, shaded to 

 white at the shorter end, and regularly stuated concen- 

 trically ; beak prominent, but scarcely central ; hinge 

 furnished with a single tooth in one valve, wliich shuts 

 into a deep cleft between two slight elevations in the 

 other. Diameter about three-eighths of an inch. 



Mem Weruerian Soc. vol. i. tab. 8. fig 4. 

 Found by Mr Laskey at Dunbar ; extremely scarce. 



Genus XXVII. Ligula. 

 Shell equivalve ; hinge with a broad erect tooth in each 



CONCHO LOGY. 





valve, projecting inwards, furnished with a pit or cavity Bivalve*. 

 for the reception of the connecting cartilage; in same — , ~Y~~ m/ 

 species a minute erect tooth. 



Obs. This genus was formed by Mr Montagu for the 

 reception of a few species, which are included by some 

 conchologists in the genera Mya and Mactra. 



1. Prcetenuis. Shell oval, thin, brittle, flat, marked PrsetemiiJ 

 with a few concentric striae ; beak small, pointed, turn- 

 ed to one side ; valves a little gaping at the smaller 



end ; hinge with a broad tooth in each valve, hollowed 

 in the middle, projecting horizontally inwards ; length 

 above half an inch, breadth one inch. 

 Test. Brit. tab. 1, fig. 2. 

 Brit. Shells, tab. 176. 

 Found in several places on the English coast. Mr 

 Laskey found it at Portobello sands, and we have seen 

 it in Zetland. 



2. Pubescens. Shell thin, brittle, oval, white, trun- Fubeseeus 

 cated at the smaller end ; behind the cartilage slope, 



one valve turns up and embraces the other valve ; beak 

 nearly central ; hinge, with one broad tooth projecting 

 inwards; length two inches long, and three inches 

 wide. 



Brit. Shells, tab. 82. 



Brit. Zool. tab. 47, fig. 26. Young. 

 Found on the Cornwall and Devonshire Coast. The 

 young shells are frequent on the Scottish coast as far- 

 north as Zetland. 



3. Dhtorta. Shell subpellucid, thin, fragile, rugged, Distorts, 

 and distorted ; valves convex ; beak small, nearly cen- 

 tral ; hinge, with a broad subtriangular tooth ; length 



an inch and three quarters, breadth two inches and a 

 half. 



Test. Brit. tab. 1, fig. 1. 

 Found on the coast of Cornwall and Devon by Mr 

 Montagu. It sometimes burrows in limestone. 



4. Compressa. Shell flat, thin, sub-oval, sub-triangu- Compressa, 

 lar, concentrically wrinkled ; beak small, central ; lunge 

 without lateral teeth ; primary teeth small, a single one 

 locking into a bifid tooth in the opposite valve ; length 



an inch and a half, breadth two inches. 



Pult. Hutch. Dorset, tab. 17, fig- 1- Mactra com- 

 pressa. 

 Brit. Shells, tab. 64, fig. 1. Tellina plana. 

 Found in abundance at the mouths of rivers, but ne- 

 ver beyond the flux of the tide. 



5. Tenuis. Shell equilateral, compressed, subtrian- Tenuis, 

 gular, semipellucid, thin, concentrically wrinkled ; beak 

 small, central, much produced ; hinge furnished with 



a bifurcated tooth in one valve, and a plain tooth in the 

 other, with a remote lateral tooth in each valve; length 

 a quarter of an inch, breadth little more. 

 Test. Brit. tab. 17, fig. 7. 

 Found by Mr Montagu at Southampton, by Mr Bry- 

 er at Weymouth, and by Mr Laskey at Musselburgh. 



6. Boysii. Shell oval, flat, thin, pellucid, almost Eoysii, 

 smooth ; beak placed near the small end, and a little 

 turned at the apex ; hinge, with small primary teeth ; 

 cartilage cavity broad ; lateral teeth in one valve only, 

 broad, elevated; length half an inch, breadth three 

 quarters. 



Test. Brit. tab. 3, fig. 7. 

 First discovered at Sandwich by Mr Boys. Mr Mon- 

 tagu has likewise found it on the coast of Devon and 

 Dorset. It is likewise common on the Portobello sands 

 near Edinburgh. 



7. Prismalica. Shell oblong, flat, thin, glossy, white, p ..; smali ^ 

 attenuated at one end, and obsoletely striated concen- 



