72 CEETACEOUS PELECYPOBA 



to tlie distinction of certain species which Agassiz described under the name of Coriwya', the 

 conclusions to which they arrive are^ however^ not in favor of a generic distinction of those forms 

 from Thracia. I shall refer to these distinctions when quoting the respective species. I may only 

 remark that^ so far as I had opportunity of examining' some of the mesozoic species^ described as 

 ThracicB, they did not appear to have the hinge margin behind the beaks inflected^ and the shell is 

 also in most cases much thinner than we usually see it in recent Thracice ; I do not think there are 

 among them many species which will finally be proved to belong to the last named genus. 



1-4. — Thracia vidvaria, Kg., Th. Nicoletti, Kg., Tk. Rohinaldina, d^Orb.^ Th. neocomiensis, 

 d^Orb.^ are all species of Corimya. 



5. — Tk. suh-depressa, d^Orb.^, is an altogether doubtful species^ and ought to be struck out of the 

 list of cretaceous fossils, 



6. — Th. siihangulata, Desh.^ appears to be a Corimya, though it is difficult to separate it 

 from Anatina, at least from the form which Agassi z called Flatymya (in parte),, and Loriol lately 

 JPlectomya. 



7. — Th. taiirica, Kg., has more the form of some recent Thracm, than that of a Corimya; no 

 posterior ribs appear to exist;, and the species may^ therefore^, be a truje Thracia. 



8. — Th. Fhillipsii, Rom.^ is a true Corimya. 



9. — Th, recurva, d^Orb.^ {Mya depressa, Phill.^ and Th. Phillipsi, Morr.,) is probably the same 

 species as the former. 



10. — Th. suhroUtndata, Piet. and Camp. (= Lyonsia suhroUindata = Fanop^a rotundata, 

 Sowerby)^ must stand as Corimya rotundata, Sow.^ sp.^ should it be proved to be different from 

 C. recurva, which is very improbable^ even should the last be distinct from C. Phillipsii. 



11. — Th. Couloni, Pict. and Ren., may be a Corim.ya, or a species of Flectomya (= ? Flatymya), 

 a sub-genus of Anatina. Pictet and Campiche consider it a doubtful species. 



12. — Th, Ricordeana, d^Orb.^ is not known by any sufficient characteristic or a figure ; the 

 reference made (Prod. 11^ p. 117J to L. Roiiyana, (under which name a species of Lyonsia was never 

 published by d^Orbigny or any other author)^ may possibly mean Anatina Roy ana, and in such 

 case it would indicate that the species in question may belong to the same genus as the former. 



13. — Th. simplex, {Periploma id., d^Orb.^) is a Corimya. 



14. — Th. SanctcB-crucis , Pict. and Camp.^ may be a true Thracia, with the margins behind the 

 beaks bent internally^ as they are not visible in fig. 8b^ 1. cit.^ pi. 108. 



15_X7. — 'FJi, rotundata, alpina and Sahaudiana, Pict. and Roux^ may all be species of Thracia, 

 but if the first should prove to be a Corimya its name must be changed. 



18-19. — Th, carinifera and elegans, d^Orb.^ may both be Thracim -, they are slightly in- 

 equivalve. 



20. — Th. Koechlina, d^Orb.^ is an undetermined species. 



21. — Th. gibhosa, d^Orb.^ has the external form of an Ixartia (= Rupicola). 



22. — Th, Sapho, Periploma id., d^Orb.^ is merely known by name. 



23-25. — Th. inornata, d^Orb., Th, Condamyi ^indi Bay lei, Coq. The first is known almost only 

 by namC;, the others are accompanied by characteristic descriptions which may be found sufficient for 

 the identification of the species. They are both strongly inequivalve^ and may with equal pro- 

 bability belong to either Periploma or Thracia, 



26. — Th. elongata, Rom.^ may be either a Thracia or any of the closely allied genera. 



27. — Th, Germari, Gieb. apud Gein.^ is very likely a Corimya. 



28. — Tellina Reichii, Romer^ (Nord. Kreidegeb., p. ix^ fig. 26), which is similar to L. recurva, 

 d^Orb., evidently is also a Corimya. D^Orbigny considered it to be a Thracia, but Pictet and 

 Campiche suggest that it may rather be a Psammolia, 



The JjMcina lenticularis apud Reuss (Bohm, Kreid.- Verst.^ pt. ii, pi. 37^ fig. 17^) seems 

 to be more allied to a Thracia than to the species described by Go Id fuss under this name. 



