14 



Family Astaetid^. Genus Kotomta. (McCoy.) (Mceonia, 

 Myonia, Pyramia, Cleobis.) 

 Shell transversely oval, sub-equivalve, inequilateral, solid, 

 slightly gaping at both ends ; hinge with one strong tooth in 

 the rifht valve, which appears to correspond to a pit in the left ; 

 two muscular impressions are large and deep ; a third small 

 accessory one is situated above the interior large one ; pallial 

 sinus very small, or only indicated by a truncation of the 

 pallial line ; ligament strong, external. (Tryon.) 



NOTOMYA GOTTLDII. (NOV. Sp.) 



Shell large, ventricose, solid, triognal, hatchet-shaped, in- 

 equilateral ; umboes gibbose ; beaks approximate ; posterior 

 slope somewhat rounded and truncate, with compressed and 

 slightly-winged margin ; anterior slope straight, longer than 

 posterior, contained angle between both slopes fully 90 deg ; 

 a deep and obliquely curved furrow or depression on both 

 valves runs from a point near the umboes, and continues to the 

 ventral margin, dividing each valve into two symmetrical wedgel 

 like lobes, and forming a somewhat deep sinus at ventral 

 margin, the anterior lobe being larger and more produced ; the 

 surface of both valves is ornamented with very coarse, irregular, 

 concentric, cord-like sulci, which follow the sinuation pro- 

 duced by the deep mesial furrow. 



Breadth, 6| inches ; length, 7 inches ; greatest depth of 

 both valves at umboes, 4| inches. Not uncommon in the 

 Maria Island limestones. (Up. Pal.) 



NOTOMI'A TRIGONALIS. (NOV. Sp.) 



Shell large, trigonal, ventricose, thickest at umboes, inequi- 

 lateral ; beaks roundly obtuse, incurved, approximate ; anterior 

 slope almost straight ; posterior slope slightly depressed and 

 produced, scarcely arched ; posterior ridge arched towards 

 anterior shoulder, obtusely rounded, and becoming obsolete 

 towards interior angle of posterior slope ; ventral margin gently 

 curved, obtusely rounded at base of posterior slope ; sharply 

 rounded, almost angled at base of anterior slope ; surface of 

 valves ornamented with regular, comparatively fine concentric 

 Strife, and with distant obsolete concentric undulations ; angle 

 contained between slopes fully 90 deg. 



Length, 5| inches ; breadth, 4 inches ; thickness at umboes, 

 3f inches. _ 



This shell approaches more closely to M. gracilis (J. D 

 Dana) than to any other form, but differs from the species 

 named in size in the straighter slopes and in the gently-curved 

 ventral margin. Western Tiers, Tasmania. 



