8 MOLLUSCA FROM THE GREAT OOLITE. 



which have no particular reference to the size of the shell. The large distant radiating 

 costae will distinguish this from P. ornatus, to which it is nearly allied. 



Locality. Minchinhampton Common, where it occurs rarely in the soft shelly Oolite 

 beneath the planking. 



Pecten, Lamarck. 



Pecten, Rumphius, Chemn., Bolten, ^c. 

 Janira, Schum, D'Orb. 

 Neithea, Brouet. 



Gen. Char. Shell regular, inequivalve, inequilateral, eared, hinge margin straight, 

 surface with radiating ribs, lines or other elevations : hinge destitute of teeth, but having 

 u central triangular pit containing the cartilage, muscular impressions one in each valve, 

 large, sub-central. 



Pecten vagans. Sow. Tab. I, fig. 12, 12a. 



Pecten vagans. Sow. Min. Con., t. 543, figs. 3,4,5, 1826. 

 — SULCATUS, Young and Bird. Geol. Yorks. 333, t. 9, f. 9. 



Testa ovatd sub-compressd, sub-aquivalvi, lamelKs imbricatd, costis raris regularibus 

 (10 — 11), valvce sinistrce angustis, squamis squamosis magnis, regularibus; dextrcs costis latis 

 confertim lamello-imbricatis ; auricidis magnis inaqualibus lineatis. 



Shell ovate, rather flattened, nearly equivalve, with imbricated lamellae ; costae few, 

 regular (10 — 11), and narrow, with regular elevated squamous folds in the left valve; the 

 right valve undulated with wide depressed costae crossed by densely arranged imbricated 

 lamellae ; auricles large, unequal, lineated. 



This shell, although so very abundant and well known, has nevertheless been 

 confounded with another very distinct species by Goldfuss, tab. 90, fig. 8, where an 

 elongated and convex shell, with few squamous costae, has unfortunately received this 

 appellation \ this latter shell, which is from the Lias of Bavaria, has only a remote resem- 

 blance to Pecten vagans. The costae of the left valve are regular, symmetrical, and have 

 the elevated phcae upon their surface regularly and rather closely arranged, the interstitial 

 spaces are narrow and slightly impressed with the plications ; the surface of the other valve 

 is nearly destitute of costae, and exhibits them faintly only and near to the border. It is 

 rare in the Upper Ragstones of the Inferior Oolite, but very abundant tlu"oughout the 

 EuUer's-earth and Great Oolite, and is usually accompanied by Ostrea acuminata and 

 Avicula echinata. It occurs also in the Cornbrash near Chippenham, Wiltshire. 



Pecten Woodwardii. Tab. I, fig. 20. 



Testd aquivalvi suborbiculari, convexd, auricidis magnis inaqualibus, tenuissime striatis ; 

 costis magnis radiantibus rotundis arcuatim divergentibus {circa 40 in ambitu), interstiis 

 angustis conformibus. 



