92 Marine Shells of the Western Coast of Florida 



Family HIATELLII) AK 



(Saxicavidae) 



Members of this family are distributed in all seas from circum- 

 polar oceans to the Indies. 



The mollusks bore into sponge, limestone, and the like, some- 

 times making deep burrows. Free individuals are anchored by a 

 byssus. 



The shells are variable m shape from adaptation to surround- 

 ings, inequivalve, usually oblong. The surface is rough, with brownish 

 epidermis. 



Genus HIATELLA Daudin, 1801 

 Hiatellai«- arctica (Linne) PL 18, fig. 122 



Alt., 13; length, 25; diam., 10 mm. average measurements of 

 undistorted specimens. Shape and proportions so modified by ex- 

 ternal conditions that adequate description is difficult. Shells chalky 

 white; thin, brown epidermis which scales off readily when dry. 

 Umbos anterior, rounded; posterior portion elongate, rostrate, gaping. 

 Irregular, concentric sculpture, rostrum defined by rough, angular 

 ridges; one cardinal tooth in each valve; two muscular impressions, 

 anterior pointed-oval, posterior irregular; pallial sinus not entire, 

 sinuated. 



Family GASTROCHAENIDAE 



Mollusks of this family are of burrowing habit. They penetrate 

 for a considerable distance into coral, shells, or limestone, or con- 

 struct a flask-shaped shelter from bits of debris and grains of sand. 

 An excavated burrow and its tunnel of communication with 

 the outside are lined with a smooth, calcareous deposit which gen- 

 erally projects its distal extremity a few millimeters beyond the 

 stone or shell, like a little stovepipe from a roof. Many individuals 

 may burrow into one piece of coral in association with Lithophaga 

 and Rupellana. 



The shell does not entirely enclose the animal's body, it is thin 

 and fragile, white, equivalve but inequilateral. The umbos are small 

 and anterior. The valves are in contact only along dorsal and pos- 

 terior borders, yawning widely at the ventral border. The hinge is 



^®- Lat., hiat, cleft, opening; clla diminutive. 



