70 MALONE JURASSIC FORMATION OF TEXAS. [bull. 266. 
differs from Pt. hoeneni also by its much smaller size, and in the 
absence of small downward-pointing chevrons at the apices of the 
middle and lower of the large upward-pointing ones. 
The species is named after Doctor Stanton, who first recognized 
its genus on seeing it in my collection at Sierra Blanca, Tex., he 
having previously ascertained that Pholadomya ragsdalei Nobis 
belongs also to Ptychomya. Doctor Stanton has recently shown me 
two casts of the latter species on which the hinge characters of the 
left valve, as described and figured by Pictet and Campiche, a are well I 
displayed. 
The Ptychoniya' hitherto described, so far as known to me at this 
time (1899), are as follows: 
Ptychomya robinaldina (d'Orbigny), 1843, Pal. Fr., Terr, ('ret., vol. 3, p. 75, pi 
264, figs, in- 13. 
Ptychomya solita (d'Orbigny), 1851, Rev. et Mag. de Zool., 2d series, vol. 3 
I». 381, pi. in. figs. :;. 1. 
Ptychomya sp. Unnamed. Described and figured, 1857, by Pictet and Ren] 
vier in Pal. Sr.isso. Terr. Aptien de la Perte du Rhone, et Ste. Croix, p. 90' 
pi. 11. figs. 2a, lib. 3a, 3b, as of. Pt. robinaldina (d'Orb.), but removed from 
the latter by Pictet and Campiche in 186(5 (Pal. Suisse, Foss. Terr. Cret 
Ste. Croix, p. 357), and placed near /'/. neocomiensis (de Loriol) either a:: 
a variety of the latter or a distinct species. 
Ptychomya buchiana (Karsten), 1858, Geognost. Verhiiltn. des Westl. Cohunb 
Berieht 32 ste Versamml. Deutsch. Naturf. u. Artze, p. 113, PI. V, figs. 7a, 7t 
Ptychomya neocomiensis (de Loriol), 1801, Descr. des Anim. Foss. du Mom 
Saleve, p. 71, pi. '.>, ti.^s. 1-4. 
Ptychomya <la<!<ih<i Coqnand, 1866, Mon. Pal. de I'Etage Aptien de l'Espagne 
1». 127, PI. XX. figs. 1. 2. 
Ptychomya germani Pictel and Campiche, I860, Pal. Suisse, Terr. Cret. de Stt • 
Croix, p. 354, PI. ('XX VI I, figs. 7, 8. 
Ptychomya complicata (Tate), 1867, Quart. Jour. Geol. Soc. London, vol. 23, Pr 
I. p. 1(30, PI. IX, fig. 8. 
Ptychomya zitteli Dames, 1873, Zeitschr. Deutsch. Geol. Gesellsch., vol. 25, i 
380, PI. XII, bus. 1, 2. 
Ptychomya sp. Unnamed. Described and figured, 1882, by Fran/ Tenia ii 
Denkschr. Kais. Akad. Wissensch. Mat.-Nat. CI., lid. XLIV, 2te Abth., | 
35, PI. IV. fig. IS. Regarded by Toula as probably identical with P. 
neocomiensis, though ho notes differences. It seems to me to be separate 
by its strongly arched principal costse and dorsal border, as well as by il 
size. 
Ptychomya koeneni Behrendsen, 1892, Zeitschr. Deutsch. Geol. Geselsch., vo 
44, p. 23, PI. II. fig. 4, aiid pi. •">, figs. 8a, Sb. 
Ptychomya nt<is<l<itei (Cragin), 1895, Colorado College Studies. V, p. 58. 
In addition to the above, a species of Ptychomya has been reportel 
by G. Steinmann 6 as occurring in the Cordilleras at Chilian, Chil< 
possibly in the same bed with Trigonia trttnxitoria Steinmann. Th: • 
Trigonia occurs also at Caracoles, Bolivia, from an unknown horizo 
"Pal. Suisse, Terr. Cret. de Ste. Croix, p. 351, PI. ("XXVII, fif,'s. 9d, 9e. 
6 Neues Jahrbuch f. Min., etc., 1882, vol. 1, p. 224. 
