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EOCENE MOLLUSCA. 



SCROBICULABRA. S. Wood. 



When Mr. Morris described S. Condamini he was at a loss to know in what genus 

 to place it ; and not being able to see the hinge, he referred it provisionally to 

 Psammobia. 



M. Deshayes, in describing Thracia Bazini, considered it as not improbably the same 

 shell as that described by Prof. Morris as Psammobia Condamini, although presenting some 

 differences in exterior form which induced him to give it provisionally under a different 

 specific name ; and being, for a similar reason as that which influenced Mr. Morris, 

 uncertain as to the genus he preferred rather to place it among Thracia. 



Mr. Meyer has sent me several valves of Condamini, but they are all of them so 

 fixed with the interior downwards in the indurated material as to preclude the 

 possibility of the hinge being seen, but a single specimen of a shell so closely resembling 

 Condamini in its peculiar external form as to leave little doubt of its being another 

 species of the same genus has had the hinge worked out, so as to show pretty nearly its 

 true characters ; and I find that this does not correspond with the hinge of either of the 

 genera to which Condamini has been thus referred, nor indeed does it strictly accord 

 with any genus known to me. It will be seen from the specimen of DuhcicMensis 

 figured (which is the right valve) that the hinge has a depression for the cartilage or 

 connector sloping towards the posterior side, and there is also a very small slit at the 

 umbo through which probably the cartilage protruded, and a similar slit may be seen 

 in the genera Thracia, Scrobicularia, and Abra. Our fossil has also two large cardinal 

 teeth diverging from the umbo at different angles ; but it has no lateral teeth, and in that 

 respect it differs from Abra; and although it has not quite so large or expanded a 

 depression for the cartilage as Scrobicularia, yet in respect of its hinge it corresponds 

 most nearly with that genus, appearing to be intermediate between it and Abra, having 

 probably the habits of the former. I have in consequence erected the genus Scrobicidabra 

 for its reception. Mr. Bott's specimen has unfortunately the interior nearly filled with 

 indurated material, which obscures the muscle marks ; and as this cannot be removed 

 without danger to the integrity of the specimen, I am unable to give a proper diagnosis 

 of the genus in question, and therefore prefer, beyond what is said above, not giving any 

 rather than what might prove a partially incorrect one. The interior connector, like those 

 oiMactra, Mya, and Thracia, has a slight extension outwardly, as if in those genera the 

 compression and expansion of the cartilaginous connector were not quite sufficient for 

 the purpose of the animal, without the assistance more or less of the external ligament 

 to enable it to keep the margins apart. 



