572 Systematic Paleontology 



Subgenus PYCNODONTE Fischer de Waldheim 

 [Bull. Soc. Moscow, vol. viii, 1835, p. 118, pi. i, fig. 20] 



Type. — P. radiata Fischer de Waldheim. = Ostrea vesicularis 

 Lamarck. 



" Shell free, regular, inequivalve, auricidate. Eight valve more or less 

 inflated, its summit inclined on the left valve, which is flat. Hinge 

 almost straight, ornamented on both sides of the elongated cardinal fosset 

 with numerous parallel denticulate corrugations. The fosset of the right 

 valve is deep and directed toward the interior, that of the left valve less 

 deep, triangular and turned outward." — Fischer de Waldheim, 1835. 



The subgenus is characterized by the series of corrugations on either side 

 of the ligament area. 



A. Right valve not concentrically lamellated. 



1. Altitude of adult shell usually exceeding 50 mm. Submarginal 



vermicular sculpture not conspicuously developed. 



G. fPycnodonte) vesicularis 



2. Altitude of adult shell rarely exceeding 50 mm. Submarginal ver- 



micular sculpture conspicuously developed. .G. (Pycnodonte) pusilla 



B. Right valve concentrically lamellated G. (Gryphwostrea) vomer 



(iuYi'ii.KA (Pycxodoxte) VEsict'LARis (Lamarck) 



.... Knorr, 1768, Mertw. Nat. 4, fig. 2. 



.... Faujas, 1799, Hist. Nat. de la Monte St. Pierre de Maestricht, pi. xxii, 



fig. 4; pi. xxv, figs. 2, 5. 

 Ostrea vesicularis Lamarck, 1806, Ann. du Mus. Nat. Hist., vol. viii, p. 160, 



No. 5. 

 Ostrea vesicularis Lamarck, 1809, Ann. du Mus. Nat. Hist., vol. xiv, pi. xxii, 



fig. 3. 

 .... Smith, 1816, Strata identif. Organized Fossils, p. 7, pi. iii, figs. 5-7. 

 Ostrea vesicularis Lamarck, 1819, Animaux sans Vert., vol. vi, p. 219, No. 



28. 

 Ostrea convexa Say, 1820, Am. Jour. Sci., vol. ii, p. 42. 

 Ostrea vesicularis Brongniart, 1822, Envir, de Paris, pi. iii, fig. 5. 

 Ostrea vesicularis Nilsson, 1827, Petrif. Suecana, p. 29, No. 2, pi. vii, figs. 



3-5; pi. viii, figs. 5, 6. 

 Gryphwa convexa Morton, 1828, Jour. Acad. Nat. Sci., Phila. 1st ser., vol. vi, 



p. 79, pi. iv, figs. 1, 2. 

 Gryphwa mutabilis Morton, 1828, Jour. Acad. Nat. Sci., Phila. 1st ser., vol. 



vi, p. 81, pi. iv, fig. 3. 

 Gryphwa convexa Morton, 1830, Am. Jour. Sci., 1st ser., vol. xvii, p. 283. 

 Gryphwa mutabilis Morton, 1830, Am. Jour. Sci., 1st ser., vol. xvii, p. 283. 



Etymology: irvKvos, dense, crowded: 6Sovs, tooth. 



