F. B. Meek on the Family Pteriide. 213 
representatives of this and some of the allied groups.” For in- 
stance, no conchologist could be for a moment in doubt whether 
more properly to the Aviculide or to the Pectenide, Yet In 
tracing these two families by their fossil shells back into the 
types, it will be observed that the hinge plates, or denticles, 
me more and more oblique, until in some of the Paleozoic 
obscure divisions are to be seen at the remotest extremities of the 
hinge, ranging nearly or quite parallel to the cardinal margin, as 
in Prerinia, Bakevellia, and some of the other genera apparently 
belonging to the Aviculide. In addition to this, in many © the 
etal of these ancient types, is provided with cartilage furrows, 
ay Purl ies. of Bake: 
Sion; and yet in all their other known characters these forms 
agree with the Aviculide. : iin 
Tn another direction, some of these ancient groups of Avicult 
2 . 
_ * Whether the introduction, and gradual dying out of the various forms present- 
ing these intermediate shibastihe Sian 9 from the operation of a law of patie 
like that termed by Dr. Darwin “natural selection,” or any other, or from repea 
culous creati it is ject of this paper to discuss. 
* As typitied ‘or Deadianeagide Sowerby, rehich must no as the 
Mg of Dolabra, since Prof. King has separated from that genus as f t pro rm 
oe rig Schizodus, Dolabra? alpina Hall, (Iowa Report, 1, part ii, pl. 29 fig. 2) 
Am. Jour. Sc1.—Srconp Series, Vou. XXXVI, No. 110.—Marcn, 1864. 
28 
