26 TER3IS USED 



straight, the margins of the valves being parallel to each 



other, as Solen Vagina and Siliqna. 

 Linearis-subarcnatiis is long and a little bent, with the margins 



parallel, as Solen Ensis. 

 Navindaiis is boat-shaped, as Area Noce. 

 Semi-orhicidatus is shaped like half a globe, as Chama orhiculaia. 

 Cordatus is when the valves together nearly form the shape of 



a heart, as Cardium Isocardia. 

 Triangnhis-cordatus is between triangular and heart-shaped, 



as Donax Scortum. 

 Triangulus-rotundatus is between triangular and round, as 



Venus castrensis. 

 Sub-rhomboideus is somewhat like a rhomboid, as Area lactea. 

 Trapezius is irregularly four-sided, as Chama trapezia. 



(Sub being prefixed to any term, means rather, or a little. 

 Ob, when prefixed to any term, means about.^ 



OF COIMPRESSED FORMS. 



Orbiculalus is round and flat, as Anomia Placenta. 

 Sub-rotundus is somewhat round and flattish,as MaetraListeri. 

 Lentiformis is round like a lentil, slightly convex on each 



side, with a sharp edge, as Venus tigerina. 

 Ovatus, egg-shaped, is broader at one end than the other, as 



Tellino planata. 

 Ovalis, oval, differs from ovatus in having the two ends equal, 



or nearly so, as Tellina Gari. 

 Oblongus is longer in proportion to the breadth, and more like 



