40 



Shell very minute, thin, obliquely oval ; hinge line 

 straight, narrow, with 3 or 4 teeth oblique at extreme 

 corners ; surface of valves ornamented with fine radial 

 ridges, and crossed by lines of growth ; towards the margin 

 the ridges are lamellar, and are also imbricated where inter- 

 sected by the concentric lines of growth ; margin finely 

 crenulate ; long, omil., lat. 2:fmil ; thickness at umbo of both 

 valves IJmil. Eare, Table Cape. This shell is not unlike 

 Limatula suhauriculata in general appearance, being decidedly 

 longer than broad. It differs materially from the young state 

 of C. Corioensis, McCoy. 



MyODORA AtJSTRALIS. 71.S. 



Shell trigonal, oblong, rounded margin ; angle between 

 slopes 118 ^ ; posterior slope considerably produced, almost 

 horizontal, and abruptly truncately angled at outer margin 

 of sinus area ; sinus area distinctly angled flabellate ; left 

 valve ventricosely convex, with about 54 fine rounded con- 

 centric ridges ; outer shell layer arranged in more or less 

 regular radial rows, and composed of transverse linear-oblong 

 microscopic cells, which become larger and less linear as they 

 approach margin ; right valve slightly convex, sharply and 

 irregularly concentrically ridged, angled at distinctly marked 

 sinus area ; apical angle of sinus area 28 *^ . Long. 14mil., 

 lat. 17|mil., thickness of both valves Gmil., margin of sinus 

 area 6mil. Common, Table Cape. Var. A. more finely ridged, 

 and a smaller shell ; contained angle between slopes, 110 ^ . 

 A very common shell, variable in size, but generally within 

 the limits of the above varieties. 



MyODORA iEQUILATERALIS, U.S. 



Shell (right valve only) solid, trigonal, equilateral ; 

 anterior slope scarcely rounded ; posterior slope almost 

 straight, not abruptly angled at margin of sinus area ; 

 contained angle between slopes, 90 ^ ; sinus area almost 

 obsolete ; valve slightly concave behind imibo becoming 

 moderately convex towards the middle ; yentral surface 

 closely concentrically ridged or striated throughout ; surface 

 layer composed of fine microscopic cells, which are very 

 minute, linear oblong near umbone, and are arra^iged in 

 undulating concentric lines only. Cells round and granular 

 towards margin. Long. 22mil., lat. 27mil., alt. right valve 

 3mil. Rare, Table Cape. Only one valve of this species 

 found. It is very distinct from any other species known to 

 me. It is readily distinguished by its size and its equilateral 

 almost straight sloj^es. 



Mytilicardia platycostata, n.s. 



Shell oblong, ovate, inequilateral, ornamented with 12 



