PANDORA. 



Lamarck, Hist. Mat. des Anim. sans vert. V. p. 49S. 

 Sowerby, Genera of SJiells, No. II. 



Testa transversa, ineequivahis, incequilateralis, latere postico longiore; valva altera plana. 



margine postico superiore dejlexo, dente unico, oblongo, obtuso, antico ; altera depresso- 



concavd, edentulu. Ligamentum internum, cicatriculce elongate in utrdque valva 



affixum. Impressiones musculares in utrdque valva dues, distantes, laterales. 



Species nonnullee in valva plana laminam internam, submarginalem, posticam, ab umbone 



usque ad impressionem muscularem posticam, decurrentem habent. 



Shell for the most part transversely oblong, inequivalve, inequilateral, the posterior side 

 being the longer, and slightly gaping at its extremity.* One of the valves is flat, its posterior 

 and upper margin turned inwards, and having a single, oblong, obtuse tooth on the ante- 

 rior side of the hinge ; the other valve is depresso-concave, without teeth ; but an indistinct 

 cicatrix or mark, against which the tooth of the flat valve lies when the valves are closed. 

 Ligament internal, fixed to a rather lengthened cicatrix or scar in each valve, inclined towards 

 the posterior end of the shell. 



Several of the species have in the flat valve an internal, submarginal lamina, diverging 

 from the umbo to the posterior muscular impression. It is observable, that Lamarck gives two 

 teeth to the flat valve of this genus, but as he has not mentioned any one of the species that 

 have the above-mentioned lamina, he is evidently mistaken. In all the species of this genus 

 the ligament may properly be said to be divided into two portions, the first, and generally the 

 larger attached to the cicatrices in both valves, and to the posterior part close to the umbo of 

 the tooth in the flat valve ; the second, and the smaller in some species, attached in the flat 

 valve near to the posterior side of the cicatrix, and in the concave valve to the posterior edge 

 close to the umbo : in the P. ilexuosa this second part of the ligament is much the larger, and 

 is attached to the above-described elongated lamina. Muscular impressions two in each valve, 

 distant, lateral. The mantle is attached by an interrupted impression, without any sinus. 



This remarkable genus appears to be related to the Anatina? and Corbula? : to Placuna and 

 Tellina I do not discern even the slightest proximity. A single fossil species has lately been 

 discovered in the Calcaire grossier, it is described by Deshayes in his Work on the Fossil Shells 

 of the Environs of Paris. Two recent species only have been described by Lamarck, both of 

 which are found on our coasts ; a third, namely, the P. ilexuosa, from the Red Sea, has been 

 long known to us, and I now add descriptions and figures of four more from various localities. 

 In an Appendix to a Catalogue of Shells collected in the Australian and Polynesian groups of 

 Islands, by Mr. S. Stutchbury, I have described, under the name of P. brevis, a shell which 

 I am now convinced is rather an Anatina, inasmuch as its flat valve is destitute of the blunt 



* In my work on the Genera of Shells, I have, by mistake, spoken of this as the anterior side, in the instance of this and some other 

 genera. 



