DIMYARIA. 163 



Sphenia Binghami. — Bingham's Sphenia. Plate XVIII. 

 fig. 14. Upper valve flat, much smaller than the under, 

 which is convex, and incurved at the extremity, and en- 

 velopes the smaller valve; covered with a reddish-brown 

 epidermis; inside bluish- white. Half an inch broad. In- 

 habits the Devonshire coast. 



The Spheniae of Turtoii are very probably young shells of the genus 

 Mya. 



TRIBE IT. SOLENACEA. 



Shells transversely elongated, destitute of accessory pieces, 

 and gaping at the lateral extremities only ; ligament exter- 

 nal. 



Genus 64.— GLYCIMERIS.— ZawiarcA. 



Generic Character. — Transverse, gaping widely at each 

 extremity; hinge callous, destitute of teeth; ligament ex- 

 ternal. 



These shells are distinguished from Solen by having teeth at the 

 hinge, and from Saxicava by the Ugament being placed on the shortest 

 side of the shell. 



Glycimeris Sillqua. — The Pod Gltcimeris. Plate 

 XVIII. fig. 7. Transversely oblong; covered with a black 

 epidermis ; umbones decorticated; internal disk of the valves 

 white, callous, and thick. Two inches and a half broad. 

 Inhabits the North seas. 



Genus 65.— PANOPiEA.— ZawarcyJ. 



Generic Character. — Equi valve, transverse, gaping un- 

 equally at the sides; one conical primary tooth in one valve, 

 and a compressed, short, ascending callosity on each side; 

 ligament external, affixed on the elongated side of the shell, 

 over the callosities. 



The more prominent apices of the shells of this genus at once dis- 

 tinguish them from the Myte. 



Panopcea Aldrovandi. — Aldrovandus's Panop^a, 



