SYNOPSIS OF GENERA. 
lix 
1875. Geological Survey of Ohio, vol. 2, pi. 11; Palaeontology, 292, Mr. 
Meek describes Entolium Shumardianum, Winchell? (sp.), pi. 15, figs. 4 a, b = 
Pernopecten Shumardianus, Winchell (1865). Proc. Acad. Nat. Sci. Pliilad., 
xvii, 126. 
Compare P. limatus , Winchell (1865), ib., and Avicula Cooperensis (1855), Mis¬ 
souri Geol. Rep. 
1877. Mr. S. A. Miller, Catalogue of American Palaeozoic Fossils, cites Ento¬ 
lium avicula , Swallow, 1858 ( Peden aviculus ), Trans. St. Louis Acad. Sci., Coal 
Measures, and E. Cooperensis, Shumard, 1855 ( Avicula Cooperensis ), Low. Carb. 
1865. Professor A. Winchell describes the genus Pernopecten (Proc. Acad. 
Nat. Sci. Phila., 1865,* p. 125. 
The author founds the genus upon Aviculopecten limiformis, White and Whit¬ 
field, from the Burlington sandstone of Iowa. Professor Winchell also includes 
under this genus, Pernopecten limatus, and a new species from the base of the 
Burlington limestone, together with Pernopecten Shumardianus, Winchell, which 
he says is Avicula circuius , Hall (not of Shumard) with Lima ? obsoleta, Hall, 
Lima glaber, H., and mentions several European species. “ It agrees with 
“ Amussium in its sub-symmetrical ears, central cartilage-pit, and the absence of 
“radiating ridges, but differs in its straight hinge-line and lateral cartilage-pits. 
“ It is probable that in addition to the two following species, others referred 
“ to Avicula, Peterinea and more especially Aviculopecten, Amussium and Peden, 
“ will be found to possess the assemblage of characters shown in Pernopecten. 
“Lima? obsoleta. Hall (Rep. 4th [10th in error] Dist. N. Y., p. 265) = Pecten 
“ sub-obsoletus, D’Orb., is stated to have a ‘ crenulated hinge-line,’ while its 
“ external characters are quite conformable to Pernopecten. Not improbably 
“ Lima glaber, Hall, belongs to the same association. The same may be said of 
“Peden densistria, Sandb., from the Posidonomyenschiefer of Nassau; Avicula 
“ tumida and Avicula laevigata, de Koninck, from the Carboniferous limestone of 
“ Belgium, etc., etc.” [Proceedings Acad. Nat. Sci., Phila., July, 1865, pp. 
125, 126.] 
* This publication bears the imprint of July, 1865. The Geological Report of California, containing- the 
original description of Entolium, bears date of 1865, and the Preface is dated November, 1865. 
