106 MONOGRAPH OF THE GENUS GNATHODON—DALL. vol. xvii. 



SPISULA? PAR VA, Petit. 



Gnathodon 2}a7-vum, Petit, Journ. de Conchyl., iv, p. 358, pi. 13, tigs. 9-10, 1853.— 



Reeve, Coucli. Icon., xix, Gnathodon, fig. 6, 1873. 

 Rangia parva, Adams, Gen. Rec. Moll., ii, p. 380, 1858.— Conrad, Proc. Acad. Nat. 



Sci. Phila. for 1860, p. 232; Am. Jonrn. Couch., iii, Suppl., p. 30, 1868. 

 Mactra roatrata, Reeve, Conch. Icon., viii, Mon. Mactra, PI. xix,fig. 104, 1854; 



not of Philippi, Zeitschr. Mai., 1848, p. 152, nor of Spengler, 1802. 



Brisbane River, Moreton Bay, Australia, Petit. 



Specimens ofPetit's shell in the National Museum received from H. 

 Cuming- were named by the latter Mactra rostrata, Spengler. Spengler 

 cites for a figure of his species the Coiichylien Cabinet, vol. 12, tab. 242, 

 fig. 4197, but there is no such plate or figure in the volume referred to, 

 though he may have had proofs of a plate which never was published. 

 His species is quite distinct, but Reeve has figured our shell, as iden- 

 tified by Cuming, under Spengler's name. The shell is a iSpisnla, the 

 ligament being externally visible, though partly inserted in the carti- 

 lage pit. The laterals are very sharply striated. In the specimen 

 received from Cuming the lateral teeth proper are in the left valve. 



ISOCARDIA? TENUIDENS, Whitfield. 



Gnathodon? tennidens, Whitfield, Lam. Raritan Clays, p. 27, pi. 11, figa. 7-10, 

 1885. 

 This species is only known as an internal cast from the Cretaceous 

 beds known as the Plastic Clays of New Jersey. It is a thin-shelled 

 salt water bivalve, having much the appearance of an Isocardia. It 

 was but doubtfully referred to the genus Gnatlwdon by Whitfield, and 

 I believe it should be referred to the IsoGardiida\ It has nothing but 

 the prominent and distant beaks to connect it with Gnathodon. 



EXPLANATION OF PLATE VII. 



Fig. 1. Gnathodon cuneatiis, Gray, exterior of adult specimen 60 ram. long. Mus. 

 Reg. No. 60793, p. 93. 



Fig. 2. Gttrt«/(0(?oji HienrficMs, Gould, interior of specimen 23.5 mm. long. Mus. Reg. 

 No. 103899, p. 98. 



Fig. 3. Gnathodon flexmsus, Conrad, exterior of an adult specimen 43 mm. long. 

 Mus. Reg. No. 6134, p. 98. 



Fig. 4. Gnathodon Lecontei, Conrad, one of the typical specimens, the hinge some- 

 what weatherworn, length 22 mm. Mus. Reg. No. 6833, p. 96. 



Fig. 5. Gnathodon flex nosm var. Petitianus, Dall, from the typical specimen 36.5 mm. 

 long. Mus. Reg. No. 57668rt, p. 99. 



Fig. 6. Gnathodon flexuosiiSyCcmRXU, interior, the shell a little worn, the same speci- 

 men is figured at fig. 3; p 98. 



Fig. 7. Gnathodon Johnsoni, Dall, type specimen 17.5 mm. long. Mus. Reg. No. 

 107033, p. 96. 



Fig. 8. Gnathodon cuneatiis var. nasutus, Dall, interior of type specimen 34 mm. long, 

 Mus. Reg. No. 106988, p. 94. 



Fig. 9. Gnathodon clathrodon, Conrad (em.), interior of specimen 40 mm. long, from 

 the Croatan beds. Pliocene of North Carolina. Mus. Reg. No, 112296, p. 95. 



Fig 10 r;H«i/(OfZo/i c««ea<ws, Gray, interior of valve 60 mm. long. Mus. Reg. No. 

 60793, p. 93. 



