LUCINOPSIS. 135 



to the Venerida, as none of the genera of the latter family 

 have any resemblance to this siphonal condition; still it cannot 

 be lost sight of, that the three primary teeth in the left valve, 

 which appear in no tribe but in that of the Veneres, give it a 

 decided connecting link with them. 



As to the alliance of Lucinopsis with Lucina, it is not very 

 near, and principally consists in its lenticular shape, which, 

 however, is that of many of the Veneres, so that a less signi- 

 ficant appellation might have been preferable. I must likewise 

 observe, that there are some differences of shape and position 

 from either the Tellina or Veneres in the adductor cicatrices 

 of Lucinopsis, which have a slight approach to the Lucina ; 

 in other respects there is little in common between the two, 

 there being no siphonal apparatus, and a very peculiar foot in 

 Lucina. 



These remarks may induce malacologists to take into con- 

 sideration, that, the Tellinidas and Veneridae being so closely 

 allied by the intervention of Lucinopsis, it would be desirable 

 to remove Mactra into the vicinity of Cyprina, to precede it 

 and follow Cardium, in which case the line would march thus : 

 Cardiadas, Mactrida, Cyprinidce, the Venerid<B, then the 

 Donacida, the Tellinida, and their genera, &c. ; and thus, by 

 relieving the Tellinida and Venerida of the intermediacy of 

 the Mactra, perhaps a greater approach to a natural position 

 would be obtained. 



The peculiar characters of the shell of Mactra create a diffi- 

 culty with respect to natural order, as it has many features of 

 the Myadae and Anatinidae ; but the open mantle of the animal 

 will not allow it to be so near a neighbour to them as to follow 

 the Tellinid<e ; neither can it remain between the latter family 

 and the Veneres, the union of which, I think, is more naturally 

 effected by Lucinopsis, notwithstanding the anomalies that 

 exist in that genus. The siphons of Mactra are altogether 

 different from those of the Tellina ; their tubes are more con- 

 gruous with the Veneridcs, so that it might have been placed 

 immediately after the typical Veneres if the Cyprinida had not 

 intervened, which, however, cannot be severed from them, 

 merely because their siphons are so short as scarcely to pro- 



