CLASS I 



PELECYPODA 



465 



Ceromya Ag. (Fig. 738). Curdate, inflated, with ratliui' auteiidr, prosogyrous 



beaks ; hinge margin of the right valve 

 superior, edentulous, hut with a blunt 



Flc. 730. 



Fleuromya tenuistriata 

 Ag. Middle Jura, Za- 

 jaczki, Poland, i/j. 



Fu:. 737. 



Gresslya latiroxtris 

 Ag. Lower Oolite ; 

 Tannie, Sartlie. '/l- 



Fio. 73S. 



Ceromyacf. adhnsls Queiist. IMiddlt; .Jura ; 

 Kiieuttingeri, Lorraine. Hinge, i/.j. 



elongated process in front of an internal callosity. Chiefly occurring as moulds. Jura. 



Family 2. Pholadellidae Miller (eiuL-nd.). 



Shells obovate, usually attenuated behind and slightly gajnng^ hinge margin thin, 

 edentulous, ligament parivincular, external ; posterior adductor scar large. Paleozoic. 



Allorisma King. Elongate, arcuate, the jjallial line sinuated, anterior side 

 shorter, sometimes with a lunule ; sculpture strongest mesially. Carljoniferous and 

 Permian. 



Rhytimya Uhich. Elongate, sub-quadrate, concentrically waved, the waves 



stronger anteriorly ; sculj)tured on the posterior half with 

 radiating series of granules ; lunule very narrow. Silurian. 

 Pholadella and Gimitaria Hall. Devonian ; North 

 America. 



Family 3. Pholadomyacidae Gray. 

 Shell substance nacreous and cellulo - crystalline ; gills 



Plioladomya murchitioni Sow. 

 Middle Jura ; Piezclinow, Poland. 



I'lioladomya deUoidcu Ag. 

 Middle Jura ; England, l/o. 



Pig. 741. 



Plioladomya pusch i Goldf. Oligocene ; 

 Tolz, Bavaria. 2/3. 



completely united, behind, forming a septum belotv the anal chamber ; foot small, with an 



o'pisthop odium ; siphons long, united to their tips, not ivholly retractile, naked; ventral 



commissure of the m.antle ivith a pedal and an opisthopodial foramen. Shell thin, equi- 



VOL. I 2 H 



