50 



China, Australia, St. Nicholas, Zebu. Sandy mud, 10 fathoms, 

 Mr. Cuming. 



14. P. ASPER. (pi. xix. f. 196, 197.) nobis. 



T. sub-rotund ata, sub-compressa ; auriculis latis, obsolete 

 striatis, ralvee dextree ad marginem serratis ; valva sinistra 

 sub-complanata, versus umbones paululum elevata; costis 

 octodecim, angtdatis, prope marginem bi-angulatis, angulis 

 serratis, interstitiis angustis, planis, concentrice striatis : 

 valva dextra ventricosa, costis octodecim, rotundatis, ad 

 umbonem angulatis, concentrice striatis ; interstitiis angustis, 

 planis : colore valvse superioris pallide rubro, lineis concen- 

 tricis minutis strigato, interstitiis rubris, valvse inferioris albo, 

 lineis paucis, rubris, concentricis ; costis rubro interlineatis, 

 umbone rubrotincto. Long. 1. 40.; lat. 0. 30.; alt. 1. 20.; 

 poll. 



More flattened than any of the preceding species ; the 

 auricles are nearly equal, flat and broad, those of the lower 

 valve serrated at the margin ; the upper valve is nearly flat, 

 and very slightly elevated near the umbones ; the ribs, 

 eighteen in number, are angulated near the umbones, and the 

 tops flattened so as to form a double angle near the margin ; 

 the angles are finely serrated ; the lower valve rather ventri- 

 cose, with the ribs more rounded near the margin than in the 

 other ; the interstices in both valves are narrow and flat ; a 

 general tint of dull red is made in the upper valve by minute 

 concentric touches on the ribs, and bands in the interstices ; 

 these being less numerous and more distant in the lower valve, 

 leave it nearly white. New Guinea. (Mr. Hinds.) 



15. P. ix^QuivALVis. (pi. xix. f. 193 to 195.) ? 



Portland Catalogue. 



T. sub-rotundata, sub-compressa, obliqua, postice expansa, 

 concentrice striata ; auriculis sub-£Equalibus, parv'is ; anticis 

 minoribus ; valva sinistra sub-complanata, versus umbones 

 paululum elevata, costis octodecim, sub-angulatis, elevatis ; 

 interstitiis angustis, planis ; valva dextra ventricosa, costis 

 octodecim, elevatis, rotundatis, prope marginem sub-quadratis; 

 interstitiis, angustis, planis ; colore valvee superioris griseo, 

 brunneo-nigrescente aboque maculato ; valvse inferioris albo- 

 rufescente; costis fusco-maculatis; lateribus griseo-maculatis. 

 Variat valva inferiori rubro-maculata. Long. 1. 30. ; lat. 0. 

 50.; alt. 1. 20.; poll. 



This species, as well as the last, presents a medium between 

 those with the deep lower valve, and those which have both 

 valves deep, the upper valve of this being rather ventricose in 



