46 



upper valve has an elevation between the umbo, which is 

 concave, and the centre. This is the common British and Medi- 

 terranean Scallop Shell. Mr. Cuming has a specimen from 

 Brazil. 



2. P. similis. (pi. xvi. f. 116. 117-) nobis. 



T. P. maximo simillima, sed costis in valva, sinistra magis 

 elevatis, magis sulcatis, in valva. dextra keviuscula ; valva 

 sinistra externe concava. Long. 3. 70- ; lat. 0. 60. ; alt. 3. 

 40.; poll. 



Differing from P. maximus in having the ribs in the upper 

 valve more elevated and more deeply sulcated ; the upper 

 valve has not the same elevation near the centre. We have 

 only seen one specimen, which belongs to the Rev. F. J. 

 Stainforth. Great Britain ? 



3. P. Jacobceus. (pi. xv. f. 107. 108. and pi. xvii. f. 153.) 

 Linn. Syst. Nat. p. 1144. 



T. subrotunda, lateraliter expansa, subdepressa; valva 

 sinistra, prope umbonem concava, lateribus elevatis ; auriculis 

 latis, rectangulatis, concavis, prope marginem sulcatis ; costis 

 14 ad 16, in valva sinistra valde elevatis, rotundatis, concentrice 

 striatis ; in valva dextra valde elevatis, quadratis, valde radiatim 

 sulcatis, sulcis moniliformibus, interstitiis concentrice striatis ; 

 colore albo-lutescente, vel fusco-lutescente, fusco vel rubro 

 angulariter maculato. Long. 6. 50.; lat. 1. 75.; alt. 6.; poll. 



This British shell differs from P. maximus in the character 

 of the ribs, which in the upper valve are much raised 

 and concentrically striated, and in the lower valve are square, 

 elevated, deeply grooved, and deeply undercut. 



Great Britain ? anil Mediterranean. 



4. P. LA QUE AT US. (pi. XV. f. 101.) nobis. 



T. rotundata; valva dextra costis 7, latis, sublaevibus, 

 subquadratis, complanatis, obsolete radiatim sulcatis, utrinque 

 ad latera. tribus minoribus ; interstitiis angustatis, planis; valva 

 sinistra ignota; colore albo, ad umbonem purpureo tincto. 

 Long. 4. 20., lat. 1. 20. ; alt. 3. 50. ; poll. 



We have only the deep valve of this species. The principal 

 ribs are seven in number, broad, flattened, with subangular 

 edges ; there are also three or four smaller ribs on each side ; 

 the interstices are narrow. Brought by Capt. Dixon from 

 N. W. America. 



5. P. medius. (pi. xv. f. 102, 103, 104. pi. xviii. f. 177, 

 178.) Lam. Anim. s. Vert. vi. p. 163. P. Jati-costatus, British 

 Museum. 



T. sub-rotundata, sub-depressa, laevi ; valva sinistra plana, 



