Characters of .\vicuHpccfin, McCoy. — Cirty. 295 
these matters, to sjK-ak of . /. i^^ranosiis as the ijcnotypc. In 
anv event, the standini;- and affinity of Aviculipcctcii must bt 
determincd from ihc characters of . /. ihwttosiis. 
The generic characters of Aficnlipcctcti as observed in the 
species last mentioned are set forth in the extract already 
quoted from McCoy. Although r!ie ligament is described by 
him as being confined to a narow facet along the hinge mar- 
gin without a median cartilage pit, Eastman's Zittel speaks 
of it quite dittercntly. for in that work the ligamt-nt is said to 
lie in numerous shallow grooves radiating to the amphidetic 
margin of the area. This characterization seems to date l)ack 
to Woodward (in 1854), who describes the hinge area as flat, 
with several long, narrow cartilage furrows, slightly oblique, 
on each side of the umbones. From these diagnoses of the 
genus, that of McCoy and that of Woodward, two distinct 
lines of descent derive, according as one or the other is referred 
to. I am not aware that the genus has ever been redescribed 
upon the basis of later studies of .-/. Hc.viiosiis, or on the other 
hand, that it has been redefined from A. gra)iasiis Sowerby, 
the species dcsiomated by Woodward as the genotype. The 
fact that Woodward assumes a different species for the type 
than either of those accompanying the first descriptions, and 
assigns characters different from those observed by McCoy, 
furnishes some ground for suspicion that two genera are really 
involved ; but I am indisposed to entertain that view. The 
descriptions agree in most particulars and especially in stating 
that .ii'icitlif^cctcii is without the median resilium of Pcctcn, 
while if the narrow facet along tne hinge margin of McCoy's 
description were striated, a character which might vary in 
distinctness with dift'erent individuals, the words of Woodward 
would also seem to apply. It appears to me rather more prob- 
able that the differences indicated by the two diagnoses are to 
be connected with dift'erences in the observer, but especially 
with differences in the material ol)served, both sjjecific differ- 
ences and those due to unlike or xmecjual preservation. 
The spelling Avicuh'pecten is here adopted, and seems to 
be the only one which is etymologically correct, though doubt- 
less those who adhere without deviation to original spellings 
would prefer to retain the old form. The component names 
are both Latin words, and accor^iing to the almost universal 
