480 



LAMELLIBRANCHIA TA. 



[ENT. FOR. 



undata, see Grammysia undata. 



undulata, Hall, 1870, Prelim. Notice Lam. 

 Shells, p. 91, and Pal. N. Y., vol. 5, pi. 

 64, figs. 1-4, Chemung Gr. 



unioniformis, Phillips, 1836, (Isocardia 

 unioniformis,) Geol. Yorkshire, vol. 2, 

 p. 209, and Geo. Sur. 111., vol. 2, p. 346, 

 Coal Meas. 



varsoviensis, Worthen, 1884, Bull. No. 2 

 111. St. Mus. Nat. Hist., p. 18, and Geo. 

 Sur. 111., vol. 8, p. 121, Keokuk Gr. 



ventricnsa, see Cypricardites ventricosus. 

 ELYMELLA, Hall, 1885, Pal. N. Y., vol. 5, p. 

 50. [Ety. elymos, a case.] Equivalye, 

 inequilateral, ovate, elliptical ; anterior 

 end short, rounded ; posterior end nar- 

 rower, rounded ; beaks closely in- 

 curved ; umbo prominent; cardinal line 

 short; umbonal slope prominent'in the 

 upper part, not defined below ; surface 

 concentrically lined. Type E. nucu- 

 loides. 



fabalis, Hall, 1885, Pal. N. Y., vol. 5, p. 

 502, Ham. Gr. 



levata, Hall, 1885, Pal. N. Y., vol. 5, p. 504, 

 Ham. Gr. 



nuculoides, Hall, 1885, Pal. N. Y., vol. 5, 

 p. 503, Ham. Gr. 



patula, Hall, 1885, Pal. N. Y., vol. 5, p. 



505, Waverly Gr. 



Entolium, Meek, 1865, Cal. Geo. Sur., vol. 2. 

 [Ety. entos, inside ; leion, smooth.] If 

 synonymous with Pernopecten, then 

 the latter has priority ; but if distinct, 

 then probably it is not a Palaeozoic ge- 

 nus, as the type is from rocks of Juras- 

 sic age. 



Eodon, Hall, 1877, 1st Ed. Am. Pal. Foss., p. 

 244. Proposed instead of Microdon, 

 Conrad, which was preoccupied. 

 EOPTERIA, Billings, 1865, Pal. Foss., vol. 1, p. 

 221. [Ety. fos, dawn ; pteron, a wing.] 

 Prof. Billings said if Euchasma is the 

 same as Eopteria, then he desired Eop- 

 teria to be withdrawn from science. 

 Winged as in Pterinea, both valves 

 equally convex and gaping; ligament 

 external. Type E. typica. 



(?) ornata, Billings, 1865, Pal. Foss., vol. 1, 

 p. 307, Quebec Gr. 



richardsoni, Billings, 1865, Pal. Foss., vol. 

 1, p. 306, Quebec Gr. 



FIG. 821. Eopteria richardsoni. 



typica, Billings, 1865, Pal. Foss., vol. 1, p. 



221, Quebec Gr. 



EUCHASMA, Billings, 1865, Pal. Foss., vol. 1, 

 p. 360. [Ety. eu, well; chasma, a hol- 

 low.] Strongly convex, triangular, in- 



equilateral, equivalve, subcordiform, 

 gaping, posterior extremity flattened, 

 hinge short, ligament external. Type 

 E. blumenbachi. 



blumenbachi, Billings, 1859, (Conocar- 

 dium blumenbachi,) Can. Nat. and Geo., 

 vol. 4, p. 350, Quebec Gr. 

 ECCHONDRIA, Meek, 1874, 

 Am. Jour. Sci., 3d se- 

 ries, vol. 7, p. 445. 

 Like Aviculopecten in 

 form, but with an un- 

 symmetrical subrostral 

 cartilage pit and un- _ 



equal crenulations on cl ,ondria neg- 

 the two sides. Type lecta. Right 

 E. neglecta. 



neglecta, Geinitz, 



valve enlarged 

 g two diameters. 



(Pecten neglec- 

 tus,) Garb, und 

 Dyas in Neb., p. 

 p. 33, and Geo. 

 Sur. 



111., vol. 5, p. 

 589, Coal Meas. 



FIG. 823. Euchondria 

 neglecta. Hiuge-line 

 enlarged. 

 Eumicrotus, Meek, 1864, syn.' for Pseudo- 



monotis. 



hawni, see Pseudomonotis hawni. 

 hawni var. ovata, see Pseudomonotis hawni 



var. ovata. 



hawni var. tinuata, see Pseudomonotis 

 hawni var. sinuata. 



EUTHYDESMA, Hall, 



1885, Pal. N. Y., 

 vol. 5, p. 32. 

 [Ety. euthus , 

 straight ; desma, 

 a ligament.] 

 Equivalve, in- 

 eq u ilateral, 

 broadly subovate, 



with a subalate FIG. 824. Euthydesma 

 cardinal expan- subtextile. 



sion ; cardinal line straight ; anterior 

 end short ; surface concentrically lined ; 

 hinge-line marked by a continuous lig- 

 amental groove. Type E. subtextile. 

 subtextile, Hall, 1843, ( Astarte subtextilis,) 

 Geo. Sur. 4th Dist. N. Y., p. 245, Port- 

 age Gr. 



Exochorhynchus, Meek, 1864, Pal. Up. Mo. 

 [Ety. exochos, prominent; rhynchos r 

 beak.] This name was suggested as a 

 probable genus or subgenus to include 

 Sedgwickia altirostrata. 



FORDILLA, Bar- 

 rande, 1881, 

 A c e p h ales. 

 Etudes Loc. 

 et Comp., 

 pi. 361, and 

 Bull. U. S. 

 Geo. Sur., 

 No. 30, p. 123. 

 A minute bi- 

 valve, somewhat resembling a Modio- 

 lopsis or an Orthonotella. Type F. 

 troyensis. 



troyensis, Barrande, 1886, Bull. U. S. Geo. 

 Sur., vol. 30, p. 125, Up. Taconic. 



FIG. 825. Fordilla troyensis. 



