292 
Tlic Aincricoii Geologist. 
May, 1904. 
margin of the sliell, defined or not; ligament and cartilage confmcJ to 
a narrow facet along the hinge-margin, no medial cartilage-pit; mns- 
cnlar impressi'in and pallial scar as in Fcclcn. 
It was onl}' on seeing the fine suite of fossils from the dark '.ime- 
stonc of Lowick, Northumberland, recently presented by the Rev. Mr. 
Jenkins to Prof. Sedgwick, and now in the collection of the University 
of Cambridge, that I recognized the characters by which the great bulk 
of the so-called Pectens of the middle and upper palaeozoic rocks are 
distinguished from the true Pectens of the more recent formation and 
present sea. In the present fossils the posterior ear is largest, thus dif- 
fering in an external character from Pcctcn and approaching Aviciila, 
an affinity greatly increased by the internal structure exposed by the 
Lowick (and some Irish) specimens, showing that there is no mesial 
ligamentary pit beneath the beak as in the former genus, but. as in the 
latter, the ligament is confined to the hinge-margin, while in general 
form and little or no obliquity of the shell the resemblance of the 
species to Pectcn is so very striking that most writers agree in placing 
them in that genus. The discovery of this character fixes the zoological 
place of numerous carboniferous shells constantly varying hitherto in 
the systems between Pecten, Aviciila and Meleagrina. 
laternal Cast of Aviculipecteu (after McCoy). 
As McCoy failed to designate a type species for Avicnli- 
pcctcii, the usual course would be to assume for that function 
the one first mentioned, or A. pJamradiatus. This seems, how- 
ever, to have been done in no instance. Woodward writing 
in 1854,* three years after McCoy's genus was published, states 
that the type of Avicnlipcctcn is Pectcn granosiis Sowerby, 
though why this sepecies was taken instead of Avicnlipcctcn 
planiradiatus or A. flc.viiosiis, which I think is really the gen- 
otype, has not been ascertained. The same type species is 
• Maa. of the Mollusca, London, pt. 2, 1S54-, p. 262. 
