178 



CONCHIFERA. 



Unio. 



and rounded ; hinge and basal lines arcuated ; surface with 

 nearly obsolete, irregular, concentric wrinkles. 



Coal Shale, near Newcastle-on-Tyne, by Mr Robertson. 



13. Unio sub-triangularis. — The Sub-triangular Unio, 

 pi. LXXIII. fig. 12. 



Pachyodon sub-triangularis. Brown, Ann. Nat. Hist. Dec. 

 1843, pi. 16, fig. 6. 



Sub-triangular, rather inflated, uiubones very prominent, 

 remote, being nearly a quarter of an inch apart ; hinge-line 

 almost parallel ; basal line with an undulation ; both sides 

 rather abruptly sloping ; surface smooth, with a slight eleva- 

 tion towards the umbones. 



Ironstone Shale at Coalbrook Dale. 

 . 14. Unio Smithii.— Smith's Unio, pi. LXXIII. f. 10, 11. 



Pachyodon Smithii. Brown, Ann. Nat. Hist. Dec. 1843, 

 pi. 16, 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 Sheden. 



15. Unio Embletoni. — Embleton's Unio, pi. LXXIII. f. 6. 

 Pachyodon Embletoni. Brown, Ann. Nat. Hist. Dec. 1843, 



pi. 16, fig. 9. 



Sub-triangular; anterior side short and rouniled ; 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 Hall, from whom I received all the Unionidai from that 

 locality. 



16. Unio Heyii.— Hey's Unio, pi. LXXIII. fig. 1. 

 Pachyodon Heyii- Brown, Ann. Nat. Hist. Dec. 1843, pi. 



16, 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. 



Ironstone Miale at Sheden. 



Named in honour of Mrs William Hey of Leeds, an expert 

 conchologist. 



17. Unio agrestis.— The Rustic Unio, pi. LXXIII. f. 20. 

 Pachyodon agrestis. Brown, Ann. Nat. Hist. Dec. 1843, 



pi. 16, fig. 11. 



Sub-compressed, transversely elongated ; anterior side much 

 rounded, posterior side lengthened and sub-acute, descending 

 in a nearly parallel line from the umbones, 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, pi. LXXIII. fig. !). 

 Pachyodon similis. Brown, Ann. Nat. Hist. Dec. 1843, 



pi. 16, fig. 12. 



Compressed ; anterior side rounded from the umbones, 

 which are 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 Shale at Middleton, near Leeds, by T. W. Embleton, 

 Esq. 



19. Unio turgidus. — The Turgid Unio, pi. LXXIII. 

 figs. 16, 17. 



Pachyodon turgidus. Brown, Ann. Nat. Hist. Dec. 1843, 

 pi. 16, "figs. 13, 14. 



Inflated ; thickness nearly seven-eighths of an inch ; breadth 

 an inch and three-eighths; umbones prominent, set a little 

 apart ; anterior side short, slightly sub-truncate ; posterior side 

 nearly parallel above, with a truncated termination ; hinge-line 

 almost parallel, basil line with a slight flexure ; surface with 

 pretty strong irregular wrinkles. 



Coal Shale at Wakefield, by W. C. Williamson, Esq. 

 surgeon, Manchester. 



20. Unio nucleus. — The Kernel Unio, pi. LXXIII. f. 8. 

 Pachyodon nucleus. Brown, Ann. Nat. Hist. Dec. 1843, 



pi. 16,* fig. 1. 



Inflated, tranversely ovate ; umbones sub-acute and remote ; 

 hinge-iine 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 the Pentland 

 Hills, near Edinburgh. 



21. Unio Blaydsii.— Blayds' Unio, pi. LXXIII. fig. 2. 

 Pachyodon Blaydsii. Brown, Ann. Nat. Hist. Dec. IS 4.3, 



pi. 16,*' fig. 2. 



Obliquely sub- triangular, inflated; umbones prominent and 

 remote ; hinge-line nearly straight ; anterior side parallel 

 above its termination, suddenly rounded ; posterior side acumi- 

 nated, straight above, with an obliquely truncated termination, 

 sharply beaked below ; basal line ascending from a line with 

 the umbones. Length five-eighths of an inch ; breadth seven- 

 eighths ; thickness nearly half an inch. 



Coal Shale at Middleton. 



22. Unio senex.— The Old Unio, pi. LXXIII. fig. 31. 

 Pachyodon antiqutis. Brown, Ann. Nat. Hist. Dec. 1843, 



pi. 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 three-eighths of an inch. 



Ironstone Shale, Low Moore, near Bradford. 



23. Unio transversus. — The Transverse Unio, pi. 

 LXXIII. fig. 21. 



