LIOPISTHA LIBAXOTICA. 39 



Liopistha Libanotica, sp. nov. 



Plate VI, figs. 7 a, b, c. 



Nucleus ovato-oblongus, cequivalvis, valde incequUateralis ; aniice brevior, sub- 

 ventrieosus, abrupte declivis ac subrotundatus ; depressio lunularis magrna, profunda, 

 marginibus valvarum exstantibus medio divisa; postice productus, elevatus, compressus, 

 subiruncatus, paulum Mans : umbones antemediani, prominentes, lati, tumidi, incurvi, 

 maxime approximati : superficies concentrice tenuiier sulcata: ligamentum externum: 

 cardo, linen palUi et impressiones musculares ignotce. 



Cast ovately oblong, equivalve, very inequilateral; before shorter than 

 behind, rather ventricose, abruptly inclined and subrotundate ; lunular de- 

 pression large, deep, divided in the middle by the projecting margins of the 

 valves; behind produced, elevated, compressed, subtrnncate, slightly gaping: 

 umbones anterior to the middle of the valves, prominent, broad, swollen, 

 incurved, closely approximate : surface concentrically and lightly sulcate : 

 ligament external : hinge, pallial line, and muscular impressions unknown. 



Three specimens, internal casts. 



Largest : length, 102 mm. ; height, 80 mm. ; thickness, 56 mm. 



One figured : " 76 mm.; " 61mm. ; " 42 mm. 



Smallest: " 73 mm.; " 52 mm.; " 36 mm. 



As seen from the side, the form and proportions of the specimens strik- 

 ingly resemble Liopistha frequens Zittel, from the Cretaceous of Gosau (first 

 described by Zittel as Panopcea frequens*), and Poromya superba Stoliczka, 

 which, with the other species assigned by that author to the same genus, are 

 conclusively proved by Meek t to belong, not to Poromya of Forbes, but to 

 his own Liopistha, — a classification which has been adopted by Zittel. % In 

 the dorsal view, the casts are seen to be much less ventricose than superba, 

 and somewhat less so than frequens ; while the three species agree in the char- 

 acter of the lunular and dorsal areas, as do the present species and frequens n\ 

 their compressed posterior extremities. Traces of teeth are absent from the 

 casts. A short and rather wide oval cavity or pit, just behind the beaks, 

 seems adapted to the gaping and '-short and erect fulcra" (Meek, op. cit., 



* Denkschriften der Kais. A.kad., Math. Naturwisstoscli., XXIV, p. Ill, PI. i, figs. 5 a-g. Ui™, L865 

 t Invert. Cret. and Ten. Foss. of Opper Missouri Country, p. 229, Washington, 1S76. 

 % Handbueh dor Palreontologie. I. Band, 2. Abtlieilung, p. 131, Miinchen, 1881. 



