THE OSTRACODOUS GENUS BAIRDIA. 571 
This robust species is distinguished by its great size, rhomboidal 
form, and abrupt posterior slope—also, in many specimens, by the 
strong overlap of the left valve, especially on the ventral border, 
and, in consequence, by a more distinct antero-ventral curve, 
amounting almost, in some cases, to a blunt angle. 
Next to B. plebeva, this species is, perhaps, of the most common 
occurrence in Carboniferous strata. Some of the Localitzes known 
to us are given below :— 
In England and Wales. Carboniferous Limestone: River Wans- 
beck, Northumberland; Wyebourne, Cumberland; Great Ormes Head, 
Caernarvonshire ; Steeraway, Salop ; Holwell, Somerset. 
In Scotland. Carboniferous Limestone (Upper): Gillfoot, Car- 
luke, and Kennox Water (Douglas), in Lanarkshire. 
Carboniferous Limestone (Lower): Mayfield Quarry and Currielee 
Limeworks (near Dalkeith), West Mains Farm (Baads), Fullarton, 
Mount Lothian, all in Edinburghshire; Galabraes, White Baulks, 
North Mine Quarry, in Linlithgowshire; Prestongrange (Kast 
Lothian), Hillhead Quarry (Wilsontown), South Shiells, Fullwood 
(Carluke), Braidwood (Carluke), Brockley (Lesmahagow), in Lanark- 
shire; Craigenglen, Campsie, Stirlingshire ; Craigie (near Kilmar- 
nock) and Howrat (near Dalry) in Ayrshire. 
Lower Carboniferous Series: Donkin’s Quarry (near Ecclefechan) 
and Bonshawburnhead Quarry, in Dumfriesshire. 
4, Barrpra ampta, Reuss. Plate XXVIII. figs, 20-23; Pl. XXTX. 
fig. 3; Pl. XXXII. figs. 17, 18, 
B. ampla, Reuss, 1854, Jahresb. der wetterau. Ges. p. 68, fig. 7. 
B. ampla, 1859, Jones, Trans. Tyneside Field-Club, vol. iy. 
pp. 162 & 166, pl. xi. figs. 14, 19. 
B. ampla, Kirkby, 1861, Quart. Journ. Geol. Soc. vol. xvii. 
p. 308. : 
- B.ampla, Jones & Kirkby, 1875, Annals Nat. Hist. ser. 4, vol. xv. 
p. 56, pl. vi. fig. 5. 
B. ampla is not of very common occurrence in Carboniferous strata, 
though examples are found showing the punctate surface-ornament 
characteristic of the species in the Permian formation. Of the speci- 
mens figured, perhaps the valve from Whorlton (Pl. XXIX. fig. 3) 
is the most typical, having the finely arched dorsal border, with the 
convex slopes, the broad and evenly rounded anterior extremity, and 
the nearly straight ventral border of good Permian examples. 
The internal cast of a left valve from Wyebourne (fig. 23) shows 
an impression of the muscle-spot, which is formed of six small spots 
grouped round a central spot. This cast approaches B. brevis, 
J.& K,, in outline, but differs therefrom in its greater relative 
ae Localities of B. ampla. 
In England. Yoredale Rocks: Whorlton, Durham. 
Carboniferous Limestone: Wyebourne, Cumberland. 
In Scotland. Carboniferous Limestone (Upper): Levenseat, Edin- 
burghshire, 
