PERNA ORIENTALIS. 59 



Of eight lots in the Museum collections, from the Lias and Oxford Clay of 

 Europe, and bearing the names given in the synonymy above, all are pyritif- 

 erous, as are our Lebanon specimens ; and from the coincidence of the latter 

 with the European specimens in their peculiar mineralization, condition of 

 surface, and even color, all might be supposed to have come from one and 

 the same deposit. All alike seem to have lost from the test a thin outer 

 layer, portions of which are retained on a single specimen from Salins. 

 Coll. Bird. 



Locality and Position. — Unmistakably Jurassic, and probably from the 

 Ornati Clay of Mejdel esh Shenis. 



Perna orientalis, sp. nov. 



Plate VI, Ugs. 1 a, b, c. 



Testa cuneato-suhquudrata, siiliccquivalcis, altitudo lonyitudinem midto snperans, 

 antice crassa, postice courtata ct in alum brevcm produda : margo cardinalis olliquus, 

 rediusculus ; area cardinalis interna lata, canaliculis parallelis ligamentmn midtipar- 

 titum excipientibus circiter novem incavata ; canaliciiU spatiis interjectis latiorcs : wn- 

 bones terminales, acuti, adunci, appro.rinudi : niargo anticus insinualus ; sinus bgssi 

 latus, profundus, rugosiis : superficies lateralis valvarwn lamellis iucrentcuti temds- 

 simis inducta : impressio muscularis snbcentralis valde excavata. 



Shell cuneately subquadrate, subequivalve, height greatly exceeding the 

 length, anteriorly thick, behind compressed and produced into a short imper- 

 fect wing: hinge margin oblique, nearly straight; internal hinge area broad, 

 grooved with about nine parallel furrows, constituting a series, which receive 

 the many-parted ligament ; the furrows wider than the intervening spaces : 

 umbones termina-1, sharp and hooked : anterior margin sinuated ; byssal sinus 

 broad, deep, rugose : sides of the valves overlaid with very thin lamellae of 

 growth: muscular impression nearly central and remarkably deep. 



Two specimens : one nearly entire, the other a single left valve. Dimen- 

 sions of entire shell : length, 32 mm. ; height, 53 mm. ; thickness, 32 mm. 

 Dimensions of single valve : length, 35 mm. ; height, 62 mm. (originally 

 about 66 nun.); thickness, 23 mm. 



This species is proportionally much thicker in front, and has a relatively 

 wider and deeper byssal sinus than any hitherto described. As seen from 

 the side, its outline somewhat resembles P. mytiloidcs Lam., which, however, 

 in all specimens and figures known to me, is comparatively flat and thin, and 



