7 
Dr. AVlieelton Hind removes certain British sj^ecies from Avicido'pecten, 
McCoy, placing them in Pterinopecten, Hall, “ because they have a narrow 
linear hinge-plate, and the posterior is not marked off from the rest of the 
valve.” ^ Mere -width of the hinge-plate is not a generic character, and Hall 
in his definition of Pterinopecten makes no allusion to it. 
A controversy has recently arisen between ^[r. G. II. Girty and Dr. 
W. Hind as to the type species of Avicidopecten. This discussion appears to 
l)e of very secondary importance, hut Mr. Girty is simply following the usual 
j^rocedurc adopted by a very large number of Authors in assuming as the 
type “the one [species] first mentioned, or A. planoradiatus” - or whatever 
its name may he. In this step his opponent appears to agree with him l)y 
saying, in “ the ahse7ice of any definite indication, it is a good and simple 
rule to regard the first described species as the type of the genus.” ^ The 
crucial point is, as we have already observed, that McCoy gave a very clear 
and concise definition of his genus, accompanied by a diagrammatic figure, 
illustrating the structure so clearly that it appears to ])c of little moment 
what the ty])c is. 
AVe adopt the family name Aviculopectinidic formerly used by one of 
us^ in place of the sub- family term Aviculopectininm proposed by Meek 
and Hayden,^ as we believe the articular characters of Aviculopecten, 
Bellopecten, ^'c., more worthy to rank as those of a family than a snb-family. 
Meek and Hayden remark that “the Aviculopecten group .seem to form a 
kind of transition from the I'ectinidce to the JPteriklcc, and ma.y possil)ly be 
distinct from them both, though it is evidently more closely allied to the 
former than the latter.” 
The more particular characters of the Aviculopectinidm will be : — 
Pectinoid shells j)ossessing an articulus, or hinge, with or without a central 
chondrophore, but always possessing a resilium occupying a scries of linear 
transverse furrows on the articulus. 
Mr. E. PhilippP also strongly advocates the inclusion of Pecten and 
Aviculopecten in separate families. 
' Hiiul — Am. Geol., 1904, .XXXIV, Xo. 3, p. 201. 
-Girty — Am. Geol., 1904, XXXIIl, No. 5, p. 291 ; XXXV, No. 5, p. 332. 
^ Hind —Am. Geol., 1904, XXXIV, No. 3, p. 200. 
‘Etheridge, .Juiir. — Geol. Pal. O'land, &e., 1892, p. 2G5. 
^Meek and Hayden — Pal. Up. Missouri, Pt. 1, 1864, p. 49. 
Philipjji — Zeitsch. Denis. Geol. Geselh, 1900, LIV, 1 Heft, p. 74. 
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