210 pandoridte. 



P. oBTiiSA, Leach. 



Form somewhat abhreviated ; posterior end the broader, ante- 

 rior end very narrow : ventral margin most swollen behind : 

 hinder dorsal edge rectilinear, and not at all sloping. 



Plate VIII. fig. 5, and (Animal) Plate G, fig. 10. 



Solen Pinna, Mont. Test. Brit. p. 567. — Linn. Trans, vol. viii. p. 48. — Wood, 



General Conch, p. 141. — Index Testaceol. pi. 3, f. 35. 

 Pandora obtusa. Leach in Lam. (ed. Desh.), vol. vi. p. 145 — Brit. Marine Conch. 



p. 57, f. 15 SowERBY, Species Conch. Pandora, p. 2, f. 1, 2, 



3. — Deles. Rec. Coquil. pi. 4, f. 8. — Hanl. Recent Shells, p. 



48, pi. .3, f. 35 — Philippi, Moll. Sicil. vol. ii. p. 14, pi. 13, 



f. 13. 



Notwithstanding that several writers upon British conch- 

 ology have supposed this to he merely the young of the 

 preceding shell, no species of Pandora can be more radi- 

 cally different, a mere glance at the extremities at once 

 determining to which of the two a specimen belongs. To 

 prevent all chance of the recurrence of such an hypothesis, 

 we have figured the true young of the latter shell. 



The shape of P. obtusa is subrhombically subovate, and 

 never elongated, and the valves are very dissimilar and 

 unequal, the left one being strongly convex, whilst the 

 right one is actually concave ; in colour, lustre, nacre, and 

 general sculjiture it is similar to rostrata, but is decidedly 

 thinner, the flat valve being of considerable tenuity and 

 great fragility ; the elevated lines which run along the 

 umbonal ridge of that species are likewise altogether want- 

 ing, or at most but feebly evident towards the beaks, the 

 umbonal ridge itself being almost if not quite obsolete. 

 There seem generally, in adult examples, a few raised 

 delicate radiating lines towards the lower margin of the 

 concave valve ; we hesitate, however, in regarding these 



