700 



LAMELLIBRANCHIA TA. 



| OR A. 



neath the beaks, without true teeth (?) ; 

 but the hinge margin of both valves 

 zigzagged by sharp incisions, into which 

 corresponding projections of the oppo- 

 site valve fit closely; the series of 

 denticulations thus formed is contin- 

 uous, but the size of the excisions 

 diminishes before and behind the 

 beaks ; posterior adductor scar nearly 

 terminal. Type G. ohioensis, which 

 is described at the same place from 

 the Waverly Gr. 

 Grammvsia blairi, S. A. Miller, 1891, Ad- 

 vance Sheets 17th Rep. Geo. Sur. Ind., 

 p. 98, Chouteau limestone. 



famelica, Herrick, 1888, Bull. Denison 

 Univ., vol. 4, p. 36, Waverly Gr. 



herricki, n. sp. Proposed instead of G. 

 ovata, Herrick, in Bull. Denison Univ., 

 vol. 4, p. 36, pi. 3, fig. 12, Up. Snbcar- 

 boniferous. 



ovata, Herrick, was preoccupied, see G. 

 herricki. 



compressed, with a sulcus extend- 

 ing toward the basal margin. Type 

 I. truncata, which with I. elongata is 

 described at the same place from the 

 Hud. Riv. Gr. 

 ovalis, Ulrich, 1892, 19th Rep. Geo. Sur. 

 Minn., p. 242, Hud. Riv. Gr. 

 Lioptkria halli, L. nasuta, L. newberryi, 

 and L. ortoni, Herrick, 1S88, Bull. 

 Denison Univ., vol. 3, pp. 60, 01, and 

 vol. 4, pp. 29, 114, Waverly Gr., ex- 

 cept the last, which is from the Keo- 

 kuk Gr. 

 Leptodesma scutella, Herrick, 1888, Bull. 

 Denison Univ., vol. '.'>, p. 59, Wa- 

 verly Gr. 

 Limoptera, the type is L. macroptera. 

 Lyriopecten nodocostatus, Herrick, 1888, 

 Bull. Denison Univ., vol. 4, p. 32, Wa- 

 verly Gr. 

 Macrodon newarkensis, M. striatocostatus, 

 Herrick, 1888, Bull. Denison Univ., 

 vol. 4, pp. 36, 37, and M. triangularis, 

 vol. 3, p. 74, Waverly < Jr. 

 pysrimeus, Whiteaves, 1892, 

 Cont. to Can. Pal., p. 299, 

 Devonian. 

 Mathehia rugosa, Ulrich, 1892, 

 L9th Rep. Geo. Sur. Minn., 

 p. 241, Trenton (ir. 

 Mbq&LODON, Sowerby, 1827, 

 < renera of Recent and Foss. 

 Shells. [Ety. megas, large; 

 odoxi*, tooth.] Shell ob- 

 long, smooth or keeled ; 

 ligament external ; hinge 

 teeth 1x2, thick; one pos- 

 terior lateral tooth; an- 

 terior adductor impression 

 deep, with a raised margin 

 and a small pedal scar 

 behind it; beaks subspiral. 

 Type M. cucullatus. 

 subovatus. Whiteaves, 1890, 

 Trans. Roy. Soc. Can., vol. 

 8, p. 97, Devonian. 

 Modiola waverlyensis, see Myti- 



Fig. 1258.-Isch yrodonta truncata. a, Outline view of a left valve ; , , lo P s waverlyensis. 



b, internal view of same ; c, d, and e, three views of a cast. " Modiolopsjs alata, M. angus- 



tata, M. milleri, M. parva, 



Ischyrodonta, Ulrich, 1890, Am. Geo., vol. 

 6, p. 173. [Ety. isehyros, strong; odous, 

 tooth.] Short or elongated, thick bi- 

 valve shells, having small subterminal 

 beaks, with the hinge straight or 

 slightly arcuate and extended poste- 

 riorly ; hinge-plate wide and strong, 

 without posterior lateral teeth, but 

 with a strong cardinal tooth in the 

 left valve, and two nearly as strong in 

 the right; just in front of them a 

 'pair of subcircular, large and deep an- 

 terior muscular impressions, and be- 

 tween these and the teeth another 

 very small pair; posterior scar large, 

 but faintly marked, ovate, situated in 

 the postero-cardinal region ; pallial- 

 line simple ; ligament probably in- 

 ternal ; in casts the beaks are prominent, 



M.. siinulatrix, M. subparallela, Ulrich, 

 1890, Am. Geo., vol. 5, pp. 274 to 283, 

 Hud. Riv. Gr.; and M. oviformis, from 

 the Trenton Gr.; and M. oblonga, M. 

 pulchella, and M. subtruncata, from 

 the Utica Slate. 



charlestownensis, Nettleroth, 1889. Ken- 

 tucky Foss. Shells, p. 218, Up. Held. 

 Gr. 



concava, M. similis, Ulrich, 1892, 19th 

 Rep. Geo. Sur. Minn., pp. 225, 227, 

 Trenton Gr., and M. subelliptica, p. 226, 

 Galena Gr. 



dychei, S. A. Miller, 1892, Advance 

 Sheets 18th Rep. Geo. Sur. Ind., p. 77, 

 Hud. Riv. Gr. 

 Modiomorpha attenuata, Whiteaves, 1890, 

 Trans. Roy. Soc. Can., vol. 8, p. 9<>, De- 

 vonian, M. compressa, M. tumida, and 



