178 
CONCHIFERA. 
Unio. 
and rounded; hinge and basal lines arcuated; surfaco with 
nearly obsolete, irregular, concentric wrinkles. 
Coal Shale, near Newcastle-on-Tyne, by Mr Robertson. 
13. Unio sub-triangularis. —The Sub-triangular Unio, 
pi. LXXI1I. fig. 12. 
Pachyodon sub-triangularis. Brown, Ann. Nat. Hist. Dec. 
1843, pi. 16, fig. G. 
Sub-triangular, rather inflated, umbones very proinineut, 
remote, being nearly a quarter of an inch apart ,* hinge-lino 
almost parallel; basal lino with an undulation; both sides 
rather abruptly sloping; surfaco smooth, with a slight eleva¬ 
tion towards the umbones. 
Ironstone Shale at Coalbrook Dale. 
14. Unio Smithit.—S mith’s Unio, pi. LXXIII. f. 10, 11. 
Pachyodon Smithii. Brown, Ann. Nat. Hist. Dec. 1843, 
pi. 1G, figs. 7, 8. 
Sub-triangular; umbones sub-central, prominent, and 
rounded, inflected and quite close ; anterior side rounded ; pos¬ 
terior side sub-acute ; surface with transverse, rather deep, 
irregular wrinkles; breadth about a third more than its length. 
Ironstone Shale at Shed on. 
15. Unio Embletoni. —Kmbleton’s Unio, pi. LXXIII. f. G. 
Pachyodon Embletoni. Brown, Ann. Nat. Hist. Dec. 1843, 
pl. 16, fig. 
Sub-triangular; anterior side short and rounded ; umbones 
placed much to one side; obtuse above ; beaks inflected and 
sharp-pointed; hinge-line considerably arcuated; posterior 
side gradually sloping, and terminating in a narrow, sub-trun¬ 
cated, rather short beak ; surface with transverse irregular 
wrinkles. 
Coal Shale at Middleton, near Leeds. 
Named in honour of Thomas William Embleton of Middle- 
ton Ilall, from whom I received all the Unionidce from that 
locality. 
1G. Unio Heyii. —Iley’s Unio, pl. LXXIII. fig. 1. 
Pachyodon Heyii. Brown, Ann. Nat. Hist. Dec. 1843, pl. 
1G, fig. 10. 
Sub-triangular, inflated; anterior side abruptly sloping; 
posterior side gradually descending, terminating in an oblique 
sub-truncation, and slightly beaked; hinge-line arcuated; 
basal line very slightly curved ; umbones prominent, but ob¬ 
tuse and quite close at the beaks ; surface with many concen¬ 
tric wrinkles; a longitudinal, gradually widening, shallow 
groove emanates from the umbones, and terminates on the 
basal margin. 
Ironstono >hale at Sheden. 
Named in honour of Mrs William Hey of Leeds, an expert 
conch ologist. 
17. Unio agrestis. —The Rustic Unio, pl. LXXIII. f. 20. 
Pachyodon agrestis. Brown, Ann. Nat. Hist. Dec. 1843, 
pl. 1G, fig. 11. 
Sub-compressed, transversely elongated ; auterior side much 
rounded, posterior side lengthened and sub-acute, descending 
in a nearly parallel line from the umboues, which are very 
obtuse and remote; on the posterior side a longitudinal, wide, 
oblique, shallow groove takes its rise on the disc and termi¬ 
nates on the basal margin, below which there is a flexure on 
the edge; whole surface covered with very coarse transverse 
wrinkles; thickness six-eighths of an inch. 
Ironstone Shale near Sheden. 
18. Unio similis.— The Similar Unio, pl. LXXIII. fig. 9. 
Pachyodon similis . Brown, Ann. Nat. Hist. Dec. 1843, 
pl. 1 G, fig. 12. 
Compressed; auterior side rounded from the umbones, 
which aro hardly produced, but very contiguous ; posterior 
side nearly parallel, obliquely truncate, with a slightly turned- 
up beak below; hinge-line nearly straight, basal line some¬ 
what arcuated ; surface irregularly wrinkled transversely. 
Coal Shalo at Middleton, near Leeds, by T. W. Embleton, 
Esq. 
19. Unio turgidus. —The Turgid Unio, pl. LXXIII. 
figs. 1G, 17. 
Pachyodon turgidus. Brown, Ann. Nat. Hist. Doc. 1843, 
pl. 1G, figs. 13, 14. 
Inflated ; thickness nearly seven-eighths of an inch ; breadth 
an inch and three-eighths ; umbones promiuent, set a little 
apart; anterior side short, slightly sub-truncate ; posterior side 
nearly parallel above, with a truncated termination ; hinge-line 
almost parallel, basil lino with a slight flexure; surface with 
pretty strong irregular wrinkles. 
Coal Shale at Wakefield, by W. C. Williamson, Esq. 
surgeon, Manchester. 
20. Unto nucleus. — Tho Kernel Unio, pl. LXXIII. f. 8. 
Pachyodon nucleus. Brown, Ann. Nat. Hist. Dec. 1843, 
pl. 16,* fig. 1. 
Inflated, tranversely ovate ; umbones sub-acute and remote ; 
hinge-line nearly straight; anterior side a little acute, poste¬ 
rior side elongated and acuminate ; basal line sub-arcuated ; 
surface with shallow transverse wrinkles. 
Coal Shale at Woodhall, on the north side of tho Pentland 
Hills, near Edinburgh. 
21. Unio Blaydsii. — Blayds’ Unio, pl. LXXIII. fig. 2. 
Pachyodon Blaydsii. Brown, Ann. Nat. I list. I)cc. 1843, 
pl. 16,* fig. 2. 
Obliquely sub-triangular, inflated; umbones prominent and 
remote ; hinge-lino nearly straight; auterior side parallel 
above its termination, suddenly rounded ; posterior side acumi¬ 
nated, straight above, with au obliquely truncated termination, 
sharply beaked below ; basal line ascending from a lino with 
the umbones. Length five-eighths of an inch ; breadth seven- 
eighths ; thickness nearly half an inch. 
Coal Shale at Middleton. 
22. Unio sen ex. —Tho Old Unio, pl. LXXIII. fig. 31. 
Pachyodon anliguus . Brown, Ann. Nat. Hist. Dec. 1843, 
pl. 16,* fig. 4. 
Transversely elongated, sub-compressed ; umbones very ob¬ 
tuse and remote ; anterior side short, nearly straight above, 
with a cleft termination ; posterior side long, with an obliquely 
sub-truncate termination; point below' a little rounded ; hinge¬ 
line very slightly arcuated ; a pretty deep transverse furrow 
runs close to and nearly parallel with the superior margin on 
the posterior side ; basal margin with a slight hollow poste¬ 
riorly ; surface with strong transverse wrinkles, and a few 
irregular, nearly obsolete, longitudinal furrows, producing an 
antiquated appearance ; thickness threo-eighths of an inch. 
Ironstone Shale, Low Moore, near Bradford. 
23. L^nio transversus. — The Transverse Unio, pl. 
LXXIII. fig. 21. 
