96 



CONCHOLOGY. 



Bivalve*, cancellated ; beak very small, with a minute cordi- 

 s ~— Y^—' form depression; inside white; margin plain; teeth, 

 two, primary, approximate, and one remote, standing 

 transverse ; the margin where the lateral tooth is placed, 

 projects into an angle ; diameter five-eighths of an inch. 

 Test. Brit. tab. 29- fig. 7. 

 Found on the shore near Dunbar by Mr Laskey. 

 Pvsera, 26. Dysera. Shell sub-ovate, sub-cordate, with distant 



concentric, elevated, and reflected ridges, the interstices 

 coarsely striated in a longitudinal direction ; beak small 

 and much reclined ; hinge furnished with three teeth 

 in each valve.; margin crenulated ; diameter not quite 

 three quarters of an inch. 



Lister's Conch, tab. 277, 278. 

 Found in the Frith of Forth by Mr Laskey. 

 Compressa, 27. Compressa. Shell strong, thick, sub-orbicular, 

 compressed, and slightly sulcated ; epidermis yellowish- 

 broAvn ; beak prominent, turned to one side, with a 

 small lanceolate cordiform depression ; margin flat ; dia- 

 meter rarely an inch. 



Test. Brit. tab. 26. fig. 1. 1. 1. 

 Found by Mr Laskey at Dunbar. We have observed 

 it in the Murray Frith and in Zetland. 

 s-otica, 28. Scotica. Shell thick, sub-cordated, sub- compress- 



ed, with many regular, parallel, transverse ridges ; epi- 

 dermis brown; beak reclined; depression lanceolate; 

 inside white, glossy; teeth strong, oblique; margin 

 plain ; length nearly three quarters of an inch, breadth 

 nearly an inch. 



Lin. Trans, vol. viii. tab. 2. fig. 3. 

 Found by Mr M'Leay on the coast of Caithness : we 

 have found it in Zetland, the Murray Frith, and the 

 island of Arran. 

 Danmonia, 29. Danmonia. Shell thick, transversely ovate, sub- 

 Compressed, and furrowed with many equidistant strong 

 concentric ridges, which, with the intermediate sulci, 

 are quite smooth ; epidermis brown ; beak nearly cen- 

 tral and somewhat reclined ; cartilage slope linear ; de- 

 pression cordiform; margin crenulated; length an inch, 

 breadth an inch and a quarter. 

 Test. Brit. tab. 29. fig. 4. 

 Found by Mr Montagu in deep water off the coast 

 of Devon, and by Mr Laskey in the Frith of Forth. 

 Nearly allied to the preceding species. 



30. Lactea. Shell thick, heavy, lentiform, some- 

 what compressed, with thick, elevated, obtuse concen- 

 tric stria?, and slightly truncated anteriorly. 



Brit. Shells, tab. 149. 

 On the western coast of England, (Mr Donovan,) and 

 on Tyningham sands, near Dunbar, by Mr Laskey. 



31. Cassina. Shell thick, with brown lines, furnish- 

 ed with numerous transverse, recurved, acute laminae ; 

 the posterior margin crenulated and grooved behind 

 the beak; umbo reddish ; depression brown ; diameter 

 an inch and a half. 



Lin. Trans, vol. viii. tab. 2. fig. 1. 

 Found by Mr M'Leay on the coast of Caithness, and 

 by Mr Neill in Orkney. 

 €uincensis, 32. Guincensis. Shell sub-cordate, with numerous 

 close regular sharp ridges ; colour cinereous, with two 

 or three rays of purplish-brown running from the umbo; 

 the cordiform and cartilage depression purple ; margin 

 plain ; length an inch and a quarter, breadth one inch 

 and a half. 



Test. Brit, page 48. Sup. 

 Found by Mr Laskey off St Abb's Head, and by Mr 

 Bryer at Weymouth. 

 Substriata, 33. Subslriala. Shell transversely ovate, sub-pellucid, 

 white, concentrically wrinkled, and obsoletely wrought 



i.actea, 



Cassina, 



with undulated longitudinal striae; beak near one end Jiivalvej, 

 small, turning towards the shortest side ; margin plain ; *— "Y~"" / 

 length half an inch. 



Test. Brit. tab. 29. fig. 6. 



Found by Mr Laskey off the isle of May in the Forth. 



34. Subrhomboidea. Shell sub-rhomboidal, rounded Subrhom- 

 at one end, and truncated at the other, and irregularly boidea - 

 wrinkled concentrically, especially towards the margin, 

 where the ridges are prominent but obtuse ; margin 

 plain behind the teeth, projecting inwards; length half 

 an inch, breadth three quarters. 

 Test. Brit. tab. 28. fig. 2. 



Found by the same gentleman with the preceding 

 species. 



Genus XXXVIII. Isocaroia. 



Shell hearlshaped, with separated, involuted, and di- XXXVI1T. 

 verging bealcs ; the hinge formed by two flattened cardi- Isocahwa. 

 nal inserted teeik, and an isolated lateral tooth under the 

 cartilage slope. 



1. Cor. Shell sub-globose, thick, strong, nearly Cor. 

 smooth, or slightly wrinkled transversely, covered with 

 a yellowish-brown epidermis ; beaks large, prominent, 

 incurvated, not touching when the valves are closed; 

 hinge strong; teeth flattish; inside smooth, white; mar- 

 gin plain ; diameter three inches. 



Brit. Shells, tab. 134. Chama Cor. 

 Mem. Wer. Soc. vol. i. tab. 8. fig. 7- 



Found near the North Foreland by Mr Swainson, on 

 the shores of the Hebrides by Mr Agnew, and alive off 

 St Abb's Head by Mr Laskey. 



Genus XXXIX. Terebratula. 



Shell convex, equilateral, inequivalved, the largest Valve XXXIX. 

 produced into an incumbent beak, pierced with a hole, Terebra- 

 throu-gh which a ligament passes by which the shell is TULA " 

 affixed ; hinge with fwo cardinal teeth. 



1. Vitrea. Shell ventricose, hyaline; front margin Vitrea. 

 a little truncated, concentrically striated or wrinkled, 

 and minutely punctured all over; lower valve with two 

 lateral teeth, from which proceed two horizontal bony 

 spicula with a small tootli towards the base of each, 

 running three-fourths across the shell ; upper valve with 

 two lateral bifid teeth, with the beak perforated; length 

 an inch and a tenth, breadth two tenths less. 



Found in a fishing boat in Zetland; taken in deep 

 water. 



Genus XL. Nucula. 



Shell inequilateral, cquivalved, sub-triangular, hinge on XL. 

 a bent line, with numerous transverse parallel teeth, and a Nuco**. 

 cardinal tooth in each valve at the angle, not inserted, 

 beaks approximating and turned backwards. 



Obs. The genus Area of Linnaeus has been divided 

 into three genera by Lamarck, which, in our opinion, 

 are perfectly distinct and well characterised. The an- 

 gular hinge of the Nucula, the straight hinge of the 

 Area, and the arched hinge of the Pectunculus, are 

 marks of distinction too striking and obvious to admit 

 or their union under one genus. They might form a 

 very good section of the dentated divison of bivalves. 



1. Nuclea. Shell sub-triangular white, with an oliva- N uc ' ca ' 

 ceous epidermis, concentrically wrinkled and crossed 

 with numerous minute stria; umbo placed a little to 

 one side, beneath which is a cordiform depression; in- 

 side glossy silvery wlnte ; hinge angular, beset with 

 4 



