72 CRETACEOUS PELECYPODA 



til lla- distinction of certain species wiiich Agassiz described under the name of Corimya ; tin 

 ciinclusions to wliich they arrive are, however, not in liivor of a generic distinction of tliose form.- 

 \'\-i>\i\ T/u-aciii. I shall refer to tliese distinctions when ((noting the respective species. 1 may f>idy 

 remark that, so far as I had opportunity of examining some of the mesozoic species, descrilied as 

 T/iracice, they did not appear to have the hinge margin Ijchind tlie Ijcaks inflected, and the shell i> 

 also in most cases much thinner than we usually see it in recent Thracia ; I do not think there an- 

 among them many species which will iinally he proved to belong to tlie last named genus. 



l-l. — T/inicia viilvaria, Ag., Th. NicoleUi, Ag., Th. Rul'nuiUliim, d'Orb., Th. neocomiensu, 

 d'Orb., are all species of Corimi/a. 



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

 list of cretaceous fossils. 



6. — Th. suhaiirjulata, Desh., ajjjjcars to be a Corimi/n, though it is difficult to separate it 

 IVom .Inaliua, at least from the form which Agassiz called Pluti/mija (in parte), and Loriol lately 

 FlectumT/a. 



7. — Th. tiuinca, Ag., has more the form of some recent Thracia, than that of a C'orimya ) no 

 posterior ribs appear to exist, and the species may, therefore, be a 1:i-ue Thracia. 



8. — Tk. PhilUpsn, Rom., is a true Corimya. 



9. — Th. /ee«)y«, d'Orb., (3/y depressa, Phill., and Th. Phillipsi, Morr.,) is probably the same 

 species as the former. 



10. — Th. subrofnndata, Piet. and Camp. (= Lyonsia suhrofnndata = Panopaa rnhnuJala, 

 Sowcrby), must stand as Corimi/ii ro/ww^/w/^, Sow., sp., should it be proved to be dift'erent from 

 C. reciirva, which is very improbable, even should the last be distinct from C. PhiUipsii. 



11. — Th. Conloni, Piet. and Ren., may be a Coriiiu/a, or a species of PlecUnni/a (^ .' Plali/Mi/ii), 

 a sub-gemis of Anatina. Pictefc and Campiche consider it a doubtfid species. 



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

 lelerence made (Prod. II, p. 117,) to L. Uoinjana, (under which name a species of Lyonsia was never 

 ]>ublished by d'Orbigny or any other author), may possibly mean Anafina Roi/ana, and in such 

 ease 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. Sancia-cmcis, Piet. and Camp., may be a true Thracia, with the margins behind the 

 l>eaks bent internally, as they are not visible iu fig. 8 b, 1. cit., pi. 108. 



15.17. — Th. rotundata, alpina and Sabaudiana, Piet. and Roux, may all be species of Thracia, 

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



^8.19. — Tli_ carinifera and elegam, d'Orb., may both be Thraciie; they are slightly in- 



eijuivalve. 



;)(!. — Th. Koechliiia, d'Orb., is an undetermined species. 



21. — Tk. gibhosa, d'Orb., has the external form of an Ixartia (— Riipicohi). 



22. — Th. Saptko, Periploma id., d'Orb., is merely known by name. 



23-25. — Th. inoniafa, d'Orh., Th. Condamyi and Baylei, Coq. The first is known almost only 

 li\ name, tlie others are accompanied by characteristic descriptions which may be I'oimd sufficient for 

 the identification of the species. They are both strongly inequivalve, and may with ei[ual pro- 

 bability belong to either Periploma or Thracia. 



26. — T/i. eloiKjaia, Rom., may be either a Tkracia 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. 2(5), which is similar to L. recttrva, 

 .rOrb., evidently is also a Corimya. D'Orbigny considered it to be a Thracia, but Pietet and 

 Campiche suggest that it may rather be a Psammobia. 



The Lucina leniicularis apud Reuss (Bohm. Kreid.- Yerst., pt. ii, ]il. 37, fig. 17,) seems 

 to be more allied to a Thracia than to the species descrilud by Gold fuss under this name. 



