394 CRETACEOUS LAMELLl HRANCHIA. 



all cases, a very minute surface of attaclnnent ; on cacli side of tlie umbo is a 

 wing-like or ear-like extension. The early part of the shell is smooth except for 

 concentric lines or ridges and occasionally fine radial furrows ; in the adult the 

 anterior and ventral marginal parts develop broad rounded folds. The stage at 

 which the folding begins and the size and iniml)er of the folds, vary in different 

 individuals. Small folds sometimes occur on the jjosterior wing-like part. The 

 ligament-pit is sometimes straight Ixit usually curves posteriorly. 



Eight A'alve at first smooth and nearly flat, occasionally slightly concave, but 

 afterwards becoming folded like the left valve. Umbo very small. 



Affinities. — Most writers, following the example of Coquand, have united 

 (). hiiKitit, Xilsson, with 0. niiguiafd (Schlotheim),' regai'ding the former as a 

 young stage of the latter. Hennig (1894, 1897) and Vogel (1895), however, do not 



'■ Kuorr, ' Recueil. Monum. Castast, Pctrificat.,' toI. ii (17G8), p. 130, P. II, pi. Dvii, figs. 5, 6. 

 Bruguiere, 'Hist. nat. Vers et Mollusques (Eucyol. iiu'thod.), Planches,' vol. iv (1827), pi. clxxxviii, 

 tigs. 4, 5. Faujas-St.-Fond, ' Hist. uat. Mte. Ste. Pierre ' (1"99), p. 150, pi. xxiii, fig. 6. Ostracites 

 umjulatus, v. ScLlotheim, iu Leouliard's ' Tascheub. fiir Min.,' vol. vii, pt. 1 (1813), p. 112 ; 0. crista 

 iiieleagris, ScLlothem, ibid., p. 112. 0. larrn, Lamarck, ' Auiniaux sans Vert.,' vol. vi (1819), p. 216 ; 

 O. dorii/eUa, Lamarck, ibid., p. 210. ? 0. falcafa, Morton, 'Amer. Journ. Sci.,' vol. xvii (183U), 

 p. 284; vol. xviii (1830), pi. iii, figs. 19, 20. 0. larva, Goldfuss, ' Petref. Germ.,' vol. ii (1833), p. 10. 

 pi. Ixxv, tig. 1. V 0. falcafa, Morton, ' Syuop. Org. Eem. Cret. U. States' (1834), p. 50, pi. iii, fig. 5 

 Ah'HnjuHia acroclonte, Fischer de Waldheim, 'Bull. Soe. Imp. Nat. Moseou,' vol. viii (1834 — 5), 

 p. llfJ, pi. V, tig. 2. 0. larva, d'Orbiguy, ' Pal. Frau9. Terr. Crct.,' vol. iii (1847), p. 740, pi. cecclxxxvi, 

 figs. 4, 5, 8 (? 6, 7). 0. larva, Miiller, ' Petref. der Aachen. Kreidef ,' pt. 1 (1847), p. 39. 0. tegulanea, 

 Forbes, ' Trans. Geol. Soc.,' ser. 2, vol. vii (1846), p. 1.56, pi. xviii, fig. 6. 0. ponticeriana, d'Oi-yn^ny, 

 ' Voy. Pol. Slid et TOccanie. Atlas Gt'ol.' (1847), pi. viii, figs. 45, 46. ? 0. larva ?, Kner, ' Kreidenieig. 

 v. Leuiberg' (1850), p. 30, pi. v, fig. 4. 0. « ro(;a //;', Queustedt, 'Handb. d. Petrefactenkunde' (1852), 

 p. 499, pi. xl, fig. 24. 0. larva, Beyrich, ' Zeitscbr. deutsch. geol. Gesellsch.,' vol. iv (1852), p. 153, 

 pi. iv, fig. 3. ? O.frons, Kner, ' Denkschr. Akad. Wiss. Wieu, Math.-uat. CI.,' vol. iii (1852), p. 319, 

 pi. xvii, fig. 10. ? 0. larva, F&vve, ' Moll. Foss. de la Craie de Lemberg' (1869), p. 160. O. mujKlata, 

 Coquand, ' Mon. Ostrea, Terr. Crct.' (1869), p. 58 (jwW/jh), pi. xxxi, figs. 4, 5, 12—15. 0. {Alec- 

 injonla) iinijiilata, Stoliczka, ' Cret. Fauna S. India,' vol. iii tlS71), p. 470, pi. xlvii, figs. 3, 4. 0. larva, 

 Lartet, 'Ann. Sci. geol.,' vol. iii (1873), ]>. 59. Alectryoitia larva, Schroder, 'Zeitscbr. d. deutsih. 

 geol. Gesellsch.,' vol. xxxiv (1882), p. 262. 0. (Alectryonia) larva. White, ' Ostreidse of N. America' 

 (1884), p. 296, pi. xlii, figs. 7—9. 0. inujulata, Peron, ' Hist. Terr, de Craie S.E. Bassiu Anglo- 

 Parisien' (1888), p. 178. 0. (Alectryonia) larva, Griepenkerl, ' Seuon. v. Kouigslutter ' ('Palajout. 

 Abluuull.,' vol. iv, 1889), p. 33. 0. nngulata, Holzapfel, ' MoUusk. Aachen. Kreide ' (' Palaeonto- 

 graphica,' vol. xxxv, 18S9), p. 250. Alectryonia ungulata, Newton, ' Quart. Journ. Geol. Soc.,' vol. 

 xlv (1889), p. 333, pi. xiv, fig. 12. 0. nngulata, Peron, 'Descript. Brach., etc., Terr. Crct. Tunisie ' 

 (1890—91), p. 185. 0. ungulata, BiJhm, ' Palieontographica,' vol. xxxviii (1891), p. 91. A. ungulata, 

 Newton, ' Joui-n. Conch.,' vol. viii (1896), p. 136. 0. (Alectryonia) ungulata, Notliug, ' U. Cret. 

 (Majstrichtian) Mari Hills ' (' Palaont. Indica," ser. xvi, vol. i, 1897), p. 38, pi ix, figs. 4, 5. ? 0. cf. 

 larva, Quaas, ' Palajontographica,' vol. xxx, 2 (1902), p. 187, pi. xxi, fig. 12. 0. (Alectryonia) ungttlata, 

 Boule and Thevenin, 'Annal. Palt'ont.,' vol. i (1906), p. 48 [6], pi. i, fig. 5. A. larva, Krunibeck, 

 ' Palseontographica,' vol. liii (1906), p. 96, pi. vii, fig. 10. 0. (Alectryonia) ungulata, Pcthii, ibid., 

 vol. Hi (1906), p. 185, pi. xii, fig. 1. 



