138 EOCENE MOLLUSCA. 



the check-tape of a trunk, to prevent its being opened too widely. This might be so if it 

 were attaclicd to the shelh I should be disposed to attribute to it quite a contrary 

 action, and to believe that its use may be to strengthen the hinge and to prevent its 

 being squeezed too closely and broken, as is frequently the case with certain species of 

 Anatina and Thracia." The ossicle in Verticordia is convex on one side and concave on 

 the other, and the concave side fits over a tubular projection under the dorsal margin of 

 the left valve, in which the cartilaginous connector is inserted. In the right valve the 

 connector is naked or unprotected, extending backwards within the margin a little beyond 

 the ossicle joining the portion of the left valve ; this ossicle reduces the large space 

 between the two umbones, and is a partial ossification of the internal connector, appearing 

 to support the cartilage by a closer and more direct action in counteracting the contraction 

 of the adductors instead of a long lateral extension across the deep umbonal region. 

 My Crag species is thick, strong, and convex, and among about a hundred specimens 

 (good and bad) that I have collected from the Coralline Crag I have never seen one 

 fractured in the umbonal region ; its large adductors and projecting riblets must enable 

 the animal to firmly close itself Avithin the shell. The absence of the ossicle in 

 Pandora may be from the form of the valves, the upper one being somewhat convex 

 internally, by which the connector would have a nearer and more direct or vertical action. 



In my Monograph of the 'Crag Moll.,' vol. ii, p. 150, the Crag species was 

 thought to be the same as a fossil from Calabria, figured by M. Philippi under the generic 

 name of Hippagus, which I adopted. Dr. Lea, who proposed the name of Hippagus, has 

 lately sent to Mr. Jeffreys a specimen of the American fossil so called. This appears to 

 belong to the family Mytilidce, and in no way related to Verticordia. I have therefore 

 resumed the generic name proposed for this Crag shell when first figured in ' Min. Conch.,' 

 t. 639, in 1844, viz. Verticordia, and I purpose here to introduce some Eocene shells 

 in it. This name Verticordia, I should add, was employed by Dr. J. E. Gray in his 'Brit. 

 Mus. Catalogue' for 1840, and he tells me (in letter) that he merely adopted it as my 

 manuscript name; both he and myself then imagining the genus to belong to the 

 Lucinida. 



M. Fischer, in the ' Journ. de Conch.,' vol. x, p. 378, has enumerated five recent 

 species and four fossil, but this number will have to be considerably reduced. One fossil 

 that may be referred to this genus has been long known, and was described as Chama 

 argentea in 1797, according to Pecchioli, and in 1852 this shell was proposed as the type 

 of a genus by Meneghini, under the name of Pecchiolia. 



The four Eocene species I propose here to introduce are very rare and have the two 

 valves united, or at least are the casts of those shells when so existing, and the 

 interiors are not visible, though I have no doubt of their belonging to this genus, and 

 possessing the same kind of hinge as my little Crag shell. M. Deshayes has figured and 

 described one species from the Paris Basin. In the sandy formation of the Coralline Crag 

 the valves, as might be supposed, are separated and displaced, with the ossicle, of course, 



