61 



pressti, minutissime cancellated umbonibus acuminatis, margine 

 ventrali denticulato, plerumque inflexo ; auriculis parvis, 

 posticis minoribus ; valva sinistra in medio paululum excavata, 

 costis 5, magnis, elevatis, gradatim declinentibus, prope 

 ttmbones angulatis, prope margimen inflatis ; valva dextra sub- 

 ventricosa, costis 4 magnis, elevatis, latis, rotundatis ; colore 

 pallidissime rufo, maculis rubris parvis, et fuscis radiatis vari- 

 egato ; valvae dextraj albo. Long. 1. 10.; lat. 0. 35.; alt. 1. 

 20. poll. 



This sliell differs from P. Danicus, in being much narrower, 

 and more elongated towards the umbones; having the margins 

 generally inflected, the ribs larger and deeper, and the 

 upper valve concave. We believe P. flexuosus, figured in the 

 same plate of Poli's work, to be a variety of this Mediterra- 

 nean species. Sicily. 



48. P. danicus. (pi. xii. f. 16. and pi. xvii. f. 187.) 

 Chemn. Conch. 11. t. 20/. f. 2043. Including P. Pseudam- 

 usium, Chem. 7- 1. 63. f. 601. 602. P. aspersus, Lam. Ostrcea 

 bvbrida, Gmel. 



T. compressa, sub-circulari,suba3quilaterali,leevi vel radiatim 

 obsolete striata ; costis septem, latis, pauxillulum elevatis, 

 gradatim declinentiljus, angulatis, prope marginem 6A r anidis ; 

 colore pallide rubro, maculis rubris, parvis, numerosis, varie- 

 gato, vel fusco, obsolete maculato. Long. 1. 60.; lat. 0. 43.; 

 alt. 1. 60. ; poll. 



A compressed, somewhat equilateral species. The general 

 surface is smooth, obsoletely striated, with seven very slightly 

 raised angular ribs, which are fainter near the margins. The 

 colour is pale red, sprinkled with minute irregular spots of 

 darker red. A variety occurs of a dull brown colour. 



Scotland, Denmark ? 



49. P. dist.vxs. (pi. xiii. f. 46, and pi. xviii. f. 182.) 

 Lam. Anim. s. Vert. \\. p. 169. 



T. sub-ovali, sub-compressa, sub-requilaterali, radiatim 

 striata ; cardine oblique plicato ; auriculis sub-a?qualibus, 

 anticis ad basin emarginatis ; costis decern, rotundatis, elevatis^ 

 crassis ; colore griseo, maculis et fasciis fuscis, nigrieantibus 

 variegato ; intus fusco. Long. 1.54.; lat. 0.61.; alt. 1. 87- ', 

 poll. 



Rather oval, rather flattened, nearly equilateral, radiatelv 

 striated ; hinge obliquely plicated ; auricles nearly equal, 

 narrowed at the base ; the ribs, 10 in number, are rounded, 

 elevated and thick ; the colour is a light cream, with bands 

 and spots of a very dark brown, inside brown. Specimens 



