40 SYEIAN MOLLUSCAN FOSSILS. 



p. 229), — in this species probably continued internally, — -which supported 

 the external ligament in the typical Liopistha. The lunular region is peculi- 

 arly and rather deeply excavated, distinctly circumscribed, and divided in 

 the middle by the projecting anterior margins of the valves. The greatest 

 thickness of the casts is below the umbones, on the vertical line which divides 

 the anterior from the second third ; and from the thickest portion the casts 

 thin gradually behind and downwards. The very thin shell gaped slightly 

 behind, and still less, or not at all, in front, while it is evident from one of 

 the two casts, which reflect unmistakably the external characters of the thin 

 test, that the valves were concentrically lightly furrowed and ridged, agree- 

 ing in this respect with Meek's section Psilomya, b. 



Conrad's brief description of his Tnoceramus Lynchii (Official Report, p. 218, 

 PI. viii, fig. 47), so far as it goes, is not inapplicable to these casts, which 

 may be specifically identical with that ; but his figures, also taken from a 

 cast, so imperfectly correspond to our specimens, that on the whole we have 

 thought it best to describe and name anew. Their unlikeness to Tnoceramus 

 is obvious. 



Largest from Coll. Cong. House: the others from Coll. Merrill. 



Locality and Position. — Beirut district ; from yellow calcareous marl, 

 Turonian. 



Ceromya sinuata, sp. nov. 



Plate VI, figs. 8 a. 1>, c. 



Nucleus inflato-cordatus, triangularis, ceguivalvis (?) : fades anterior lata, irun- 

 cata, complanato-excavata, a lateribus carina rotundaia obscura sejuncta : caviositas 

 lunularis profunda, cordiformis : pars posterior subcompressa, producta, oblique trun- 

 cata : decUvitas cardinalis paululum curvata ; margo inferior plus minusve sinuatus : 

 fovea Kgamenti angusia rf elongata: umbones antemediani, anteversi ; apices involuU, 

 attenuati, approximate. Impressiones musculares ar pattiales non a/>/></ren/. 



Cast swollen-cordate, triangular, equivalve (?) : anterior face wide, trun- 

 cate, flatly excavated, separated from the Hanks by an indistinct rounded 

 keel ; lunular hollow deep and heart-shaped : hinder portion rather com- 

 pressed, produced, obliquely truncate ; hinge-slope slightly curved ; the 

 lower margin more or less sinuate; the ligamental furrow narrow and 

 long: umbones antemesial, turned forward; beaks involute, attenuate, ap- 

 proximate. Muscular and pallial impressions not distinguishable. 



