216 F. B. Meek on the Family Pteriide. 
nizing the convenience of sections or intermediate groups between 
families and genera, for it is highly probable that if we knewall 
the characters of all the species that ever existed, from the be 
gists, and typified by the existing A. Hirundo. At any rate,l 
ave never seen a specimen, nor can I remember a figure, of 
any species showing the hinge of a true Avicula, from any of our 
American Paleozoic rocks. So far as my knowledge extends, all 
the Silurian and Devonian species, the hinge in which has been 
seen, want the cartilage cavity of the modern Aviculas, and have 
9 
E 
“ 
a 
i. 
; 
the striated hinge facet, or the oblique hinge teeth, (one or the 
other or both) of Pterinia, more or less distinctly marked. 
addition to this, most of the Silurian and Devonian, and many 
of the Carboniferous species, the hinge in which is unknow?, 
resent more the external appearance of the European species 
figured by Goldfuss and others, in which the internal characters 
of Pterinia are known to exist. 
tained, from the examination of a very fine natural cast of the 10 
terior of Avicula Flabella Conrad, from the Hamilton Group, 
Cayuga Co., N. Y., that it presents all the characters of @ 
typical Plerinia. The specimen examined is a cast of # ™ 
valve, showing the impression of three rather long oblique hinge? 
teeth behind the beak, and of seven or eight shorter ones 12 
Aviculas; but Prof. Winchell describes, from the Michigan 10 
a form which he refers to the first of these species, a8 having 
long posterior cartilage facet.” at 
From all that is now known in relation to the affinities of ‘and 
shells, we may safely infer that probably all of our Silurian cae 
Devonian species, especially those of the Hamilton and Che the 
erred , 
he 
the same relations to the existing Aviculas, or Prerias, tbat the 
shese 
