PLATE XXVI. 
Fig. 1. UNIO ELONGATE. 
Unio elongata, Lam. Si/st. vi. partie 1, p. 70- 
Mya margaritifera, Mont. Test. Brit. p. 33. — Brown in Ency. Brit. vi. p. 405. 
This shell yields mother-of-pearl, and produces pearls, sometimes of considerable size and value. The river Con- 
way, in Wales, was formerly famous on account of the large and valuable pearls produced by the Unio elongata 
inhabiting it : as was also the river Irt in Cumberland, so much so, that we are informed by Camden that Sir 
John Hawkins obtained a patent for fishing them in that river. In the Scottish rivers this shell is still occasion- 
ally fished for the sake of the included pearls ; and it is said that the pearls which decorate the Scottish crown 
are native ones, and chiefly from the river Tay. 
For an account of " the Formation of Pearls," see Encyclopedia Britannica, Vol. VI. Article Conchology, page 481. 
Fig. 2. UNIO piCTOKUM. 
Unio pictorum, Brown's MSS. 
Mya pictorum, Mont. Test. Brit. p. 34 — Bromn in Ency. Brit. vi. p. 405. — Fen. Brit. Zoot. iv. pi. 43, fig. 17 — Linn. 
Tr. viii. p. 38. 
Mya ovalis, Don. Brit. Sh. pi. 89. 
Fig. 3. UNIO Batav.^. 
Unio Batava, Lam. Syst. vi. partie 1, p. 77- 
Mva Batava, Linn. Trans, viii. p. 37 — Brown in Ency. Brit. vi. p. 405. 
Mya pictorum, Bon. Brit. Sh. pi. 174 — Mont. Test. Brit. p. 36. 
Fig. 4. UNIO ovATA. 
Unio ovata. Browns MSS. 
Unio pictorum. Lam. Syst. vi. partie 1, p. 77- 
Mya ovata, Li7in. Trans, viii. p. 39 — Brorvn in Ency. Brit. vi. p. 405. 
Mya depressa, Don. Brit. Sh. pi. 101 and 122, fig. 1, 3. 
