Tertiary.} PALEONTOLOGY OF VICTORLA.. IMoIlusca. 



Plate XXVII., Figs. 3-56. 

 CUCULL^A CORIOENSIS (McCoy). 



[Genus CUCULL^EA (Lam.). (Sub-ldngd. Mollusca. Class Dithyra. Ord. Pectinacea. 

 Fam. Arcidfe.) 



Gen. Char.— Shell equivalve or nearly so, inequilateral, trapeziform, ventricose, margins 

 closed all round ; surface radiated ; beaks large, nearly median ; hinge line straight, long, with 

 a triangular flat cartikige area in each valve intervening between it and the beaks ; hinge teeth 

 ntmierous, small, and perpendicular in the middle, with a few much larger ones diverging towards 

 each end, sometimes crenulated on the sides ; posterior adductor impression bounded anteriorly 

 by a prominent shelly hood-like plate extending from the hollow of the beak.] 



Description. — Obliquely trappzoidnl, very gibbous, beaks very large, incurved 

 usually nearer to the anterior than the posterior end of hinge line; hood-plate of 

 posterior adductor small ; 4 or 5 anterior and 3 or 4 posterior oblique teeth ; small 

 middle transver.>e hinge teeth variable in size and number ; the ridge from beak to 

 posterior abdominal or respiratory angle very obtusely rounded, and angle or junction 

 of posterior margin with hinge line a little more than a right angle ; ])osterior slope 

 moderately tlattened, rest of surface moderately convex ; anterior margin rounded ; 

 ventral margin nearly straight, oblique to hinge line ; posterior margin slightly 

 tindulating', joining in the ventral margin by an obtusely rounded angle ; surface 

 radiated with fine ilat ridges, separated hy narrow impressed sulci, and each usually 

 divided hy a finer one, and granulated by close transverse lines of growth (at 1 inch 

 from beak, about 11 of the larger stria;, each divided by a .smaller one, in 6 lines); 

 inner margin coarsely toothed. Greatest length from anterior end to posterior angle, 

 3 inches; proportional depth from beak to ventral mai-gin, ^^jj ; thickness of one 

 valve at right angles to plane of margin, ^-yij j length of hinge line, ^^''jj ; length of 

 ])osterior margin, -^-qjj. 



The two living species of Cucullcea ( C. concamerata and C. 

 granulosa) of China, Nicohar, and Mauritius, do not occvir in 

 our Victorian seas, and yet this fine fossil species is one of the 

 commonest shells of the Miocene Tertiary beds near Geelong. 

 The fossil is distinguished fi-om the recent species by its much 

 greater gibbosity, thicker shell, more obtusely rounded diagonal 

 angle defining the posterior slope (■which is narrow in the recent 

 species and sharply angular near the beak), and the jjosterior 

 inferior angle is more extended obliquely, the ventral margin being 

 more oblique to the hinge line, and in the beak being rather nearer 

 the anterior end. I find the thickness (that is the measure at right 

 angles to the plane of the margins) varies considerably in difterent 

 specimens, as well as the number of the hinge teeth. It is only when 

 the surface is well preserved that the transverse stria? of growth 



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