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PALEONTOLOGY OF NEW YORK. 
. SCHIZODUS TUMIDUS. 
PLATE LXXV, FIGS. 1, 2. 
Schizodus tumidus, Hall. Prelim. Notice Lamellibranehiata, 2, p. 94. 1870. 
Gytherodofi “ “ Twenty-third Rep. N. Y. State Mus. Nat. Hist. Expl. PI. 14, fig. 19. 1872 
(title page, in error, 1873). 
Cytherodon (Schizodus) tumidus, Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. 75, 
figs. 1, 2. 1883. 
Shell of medium size, rhomboid-ovate ; length about one-fourtli greater than 
the height. Basal margin regularly rounded anteriorly, produced a little in 
the middle and sub-truncate behind. Posterior margin obliquely truncate. 
Cardinal line short, straight. Anterior end short and regularly rounded. 
Valves convex below, gibbous in the middle and above. 
Beaks at about the anterior third or fourth, prominent, rising considerably 
above the hinge-line. Umbonal slope sub-angular, bending downward in 
the middle and continuing to the posterior extremity, producing a nasute 
extension. 
Surface characters unknown. 
Muscular impression strongly marked. Pallial line distinct. 
The specimen described is a cast of the interior, having a length of 40 
mm. and a height of 30 mm. 
This species resembles S. appressa in general form, but the umbonal angle is 
less sharply defined in the cast, the beaks are larger, and the posterior muscular 
impression is much stronger and nearer to the beaks. 
Formation and locality. In the limestone of the Upper Helderberg group, near 
Columbus, Ohio. 
