53 



Syst. Nat. p. 1147. Including P. Sowerbii, Gidlding. Ostrea 

 principalis, flavellum, radiata? plana? crocea? florida? Gmel. 



T. rotundata, venticosa^ concentrice et radiatum striata ; 

 ariculis sub-sequalibus, striatis, obtusis; costis octodecim, 

 sub-scabris; valva dextra quam altera paululuni magis 

 ventricosa; colore vario. Long. 1.75.; lat. 0. 75.; alt 1.65.; 

 poll. 



Rounded, ventricose, concentrically and radiatedly striated; 

 the auricles are nearly equal, striated and obtuse ; the ribs are 

 18, rather rough ; the lower valve rather more ventricose than 

 the upper. The numerous variations in colouring seem to 

 have given rise to many of the specific names quoted above ; 

 some are dull brown, others bright red, others delicately 

 pink, mottled with brown, others of a light blue tint, variegated 

 with patches of dark brown and touches of white and yellow. 

 The variety (f. 17.) named P. Sowerbii, is from St. Vincents. 



Coasts of the Pacific. 



23. P. oPERCULARis. (pi. xvii. f. 141 to 146.) Linn. 

 Syst. Nat. p 1147. Including lineolatus. Lam. &c. 



T. rotundata, sub-ventricosa, concentrice et radiatim 

 striata ; auriculis sub-eequalibus, striatis, ^ obtusis, valvce 

 inferioris antica majuscula, basin emarginata ; valva sinistra 

 scabra quam altera majis ventricosa, costis octodecim ad 

 viginti, sub-angulatis, interstitiis latis; valva dextra costis 

 miniis angulatis, interstitiis angustioribus ; colore vario. 

 Long. 2. 50. ; lat. 0. 95. ; alt 2. 30. ; poll. 



This well known British species diifers from P. gibbus, m 

 being less ventricose and more dilated at the sides ; the ribs 

 are somewhat less elevated, and the upper valve is much more 

 ventricose than the lower. The varieties are numerous, the 

 commonest is light reddish brown, banded and variegated 

 with purplish brown, much lighter on the lower valve ; there 

 is also a bright orange variety and a white one. The variety 

 named P. lineolatus is white, with a red line on the top of 

 each rib. Great Britain and Mediterranean. 



24. P. SUB-RUFUS. (pi. xix. f. 208 to 210.) Pennant. Brit. 

 Zool. iv. p. 100. t. 60, 63. P. Audouini, Payr. Ostrcca palliata ? 

 Gmel. 



T. sub-rotundata, sub-compressa, postice sub-attenuata ; 

 scabra; auricuHs sub-eequalibus, striatis, obtusis, yalvae 

 inferioris antica majuscula, basin emarginata ; costis viginti, 

 angulatis, anguhs serratis, lateribus concentrice striatis ; inter- 

 stitiis scabroso-striatis ; colore vario. Long. 2. 50. ; lat. 0. 

 90. ; alt. 2. 40. ; poll. 



