F. B. Meek on the Family Ptertide. 217 
old Aviculopectens do to our modern Pectens.’ For, in the mod- 
ern types of the Pectenide and Aviculide, the cartilage is mainly 
Prof. McCoy, Mr. Woodward and others, in referring that genus 
also to the ‘Aviculide, had it not been for the fact, that, on sub- 
jecting sections of a typical Carboniferous species (Aviculopecten 
amplus Meek & Worthen) to a microscopical examination, it was 
found not to possess the prismatic structure of the Aviculide, but 
' 127, pl. cxvi, fig. 10, a, 6, ¢, 4 & f, 9) 
This genus may be briefly characterized as follows :— 
Genus GrypHoruyNcuvs, Meek.—Shell small, thick, nearly 
Or quite as wide as long, very slightly oblique, plano-convex, or 
sub-hemispherical, the right valve being flat or concave, and the 
left very gibbous; posterior and anterior margins, somewhat 
sinuous, but neither valve with a defined byssal sinus. Beaks 
sub-central; that of the left valve elevated, gibbous, ree 
incurved, and at the extremity directed obliquely forward ; be 
) 
shell, ranging more or less nearly at right angles to the umbonal 
axis; in both valves provided with a wide, well defined cardinal 
area. Ears subequal, not produced, i t 
and convex in the left, in which latter the anterior one 18 sepa- 
rated from the swell of the umbo by 4 deep oblique “spt 
Surface with fine, sometimes decussating strie. Hinge with sev- 
~ ral small irregular teeth near the middle. 
* The i ad between nearly or quite all of the Paleo- 
elaine woe Basile & our modern seas. 
