G»i PALEONTOLOGY OF NEW YORK. 



spines. The radii are less conspiouons on tlie ears, wliidi also show a few 

 concentric undulations. 



Internal characters not preserved. The liganiental area appeart> as a 

 simple fold in the hinge. 



The specimen has a length of 15 mm. ; height 13.5 mm. ; hinge-line 

 18 mm. 



This .species has the general form and aspect of P. Hermes and P. latus. hut 

 is proportiomilly wider, with different and characteristic surface markings. 



Formation and locality. In soft shales of the upper part of the Hamilton 

 group, shore of Canandaigua lake, Ontario county, N. Y. 



Pterinopecten conspectus. 



PLATE XVII, FIGS. 17, IS, 20, il. 



Ptj-riiu>petten votutptctiui. Hall. Pal. N. V., vdI. v, \A. 1. Plates ami Kxplanations : PI. 17, fifrs. 17-21. 



Jan., 1883. 



Shell of medium size, siih-rhom))()idal ; moderately <)l>li(|nc in young shells, 

 scarcc'ly oliliijuf in oMcr oiu's : length ami height ahout cnual, the U-ngth 

 usually a little greater; j^allial margins regularly rounded, straighter poste- 

 I'ioi'ly, and merging into the ivir without deliiiitc limitation. 



Left valve moderately convex. Right valve nearly Hat, narrower and 

 ol)li(|ue, with a deeper hyssal sinu.s. 



Hinge-line .straight, nearly central, equalling, or a little greater tlian. the 

 length of the .shell. 



Beak suh-acute, anterior to the centre of the hinge-line, directed slightly 

 forward. Urahonal region somewhat prominent, suhtending an angle of 

 ahout 75°. 



Ears triangulai-. I'osteiior one much the larger, not distinctly defined on 

 the valve; margin sligiitly concave; exti'cmity rcctauLinlar oi' somewhat 

 acute, .\ntfi-ioi' ear small, distinctly delint'd ]\\ a roundi'd miIcus ; margin 

 convex ; extremitv rounded or sul)-anirular. i}\ ssal sinus moderate in the 



