lx 
SYNOPSIS OF GENERA. 
1866. Geological Survey of Illinois, Palaeontology, vol. II, p. 334. Under 
the discussion of Streblopteria, Mr. Meek states that “ Prof. Winchell has 
proposed the name Pernopecten* (Proc. Acad. Nat. Sci., Phila., July, 1865, 
p. 125), for a somewhat similar type. That genus, however, differs in having 
a central cartilage-pit under the beaks, with smaller pits along the hinge on 
each side, while it wants the deep byssal sinus under the anterior ear of the 
right valve, seen in Streblopteria.” 
1868. Geological Survey of Illinois, vol. Ill, p. 453. Mr. Meek cites Perno¬ 
pecten, Winchell (1865), with the species P. Shumardanus, Winchell ? pi. 14, 
figs. 6 a, b, and the following synonymy : 
“ Avicula circulus, Hall, 1858, Geological Report Iowa, vol. 1, part ii, p. 522, 
pi. vii, fig. 9. Not A. circulus, Shumard, 1855, Missouri Report, pi. C, fig. 14. 
“ Pernopecten Shumardianus, Winchell, 1865, Proc. Acad. Nat. Sci., Phila., p. 126. 
“ Compare A. Cooperensis, Shumard (1855), Missouri Report, pi. C, fig. 
“ 15 = ? Aviculopecten limaformis, White and Whitfield (1862), Proc. Bos- 
“ ton Soc. Nat. Hist., vol. viii, p. 295. 
1875. Geological Survey of Ohio, vol. 2, part ii, Palaeontology; Mr. Meek 
places Pernopecten Shumardanus, Winchell, under the genus Entolium. See 
citations under the latter genus. 
1877. Mr. S. A. Miller cites in his Catalogue the following species, viz. : 
Pernopecten crenulatus, H., P. fasciculatus, H., P. glaber, H., P. limiformis , White 
and Whitfield, P. limatus, Winchell, P. obsoletus, H., P. Shumardanus, Winchell. 
From an investigation of the literature upon Pernopecten and Entolium, and 
a study of the type specimens of the former genus, it is evident that Perno¬ 
pecten has priority and includes Pecten demissus of Phillips. Entolium, if existing 
in nature, should be restricted to the species first indicated ( E . aurarium), and 
other allied forms, if any, and it is probably not found at all in the palaeozoic 
* “ The typeof Pernopecten is P. Cooperensis = (Avicula Cooperensis, Shumard,= Aviculopecten limaformis, 
White and Whitfield). The typical specimen of this species, figured by Dr. Shumard in the Missouri Report, 
shows a few obscure radiating costae—an exceedingly rare character, though we have occasionally seen 
faint indications of them on other specimens. Hence, Dr. Shumard’s species has not been g-enerally identi¬ 
fied, and Prof. Hall, in the Iowa Report, p. 522, pi. 7, fig. 9, erroneously refers apparently the same shell 
to Avicula circulus, of Shumard, a quite different species.” [Meek.] 
