86 Marine Shells of the Western Coast of Florida 



rounded in front; slightly rostrate behind; posterior margin straight, 

 directed obliquely downward, slightly gaping; umbos pointed, 

 posterior to center; concentric sculpture of numerous threadlike 

 ridges. Each valve has one small cardinal tooth, a central spoon- 

 shaped fossette and elongated anterior and posterior laterals. In- 

 terior white, highly polished; pallial sinus deep and rounded. 



('iiiiiiii§ria coarctnta^ '■" Sowerby PI. 17, fig. 108 



Alt., 11; length, 16; diam., 8 mm. Shell white, irregular, inflated; 

 thin epidermis; umbos acute, posterior to center, anterior margin 

 high and rounded, posterior margin more abrupt, slightly gaping; 

 small, concentric, definitely lamellar ridges, more widely apart than 

 those of C. tellinoides. 



Both these species of Cumingia are of nesting habit, specimens 

 are often found in cavities of sponges and clumps of debris. 



Family DOlVAt'LDAE 



Species of the genus Donax of this farnily are the most abund- 

 ant bivalves along much of the Florida Coast. Their shells are the 

 principal component of the coquina rock so extensively used in 

 building and road making in the far South. 



Their stations are in sandy bottoms of shallow coastal waters, 

 and the mollusks are no less liked in broth and chowder for human 

 delectation than by certain fish and ducks which consume them in 

 great numbers. The family is distributed through all warm seas. 



Coquinas live buried just below the surface of sandy sea bottoms 

 with the two delicate siphons projected into the water. In a quiet 

 tide pool the siphons respond to every movement of the water, bend- 

 ing and recovering like a field of grain before the wind. 



The foot of Donax is strong, sharp, and pointed, and when the 

 animals are dislodged from their shallow burrows they are able to 

 bury themselves before a succeeding wave washes them away. 



Genus DONAX Linne, 1758 

 Donax rariabilisi^s Say PI. 17, fig. 109 



Alt., 11; length, 19 mm. Shell smooth, not glossy; equivalve, 



^*** Lat., coarctare, to press together. 



^*'* Gr., donax, a dart, a sea scallop; variabiiis, variable. 



