Pectinidae and Limidae 49 



ters; right valve more deeply concave, humped In umbonal region; 

 upper valve mottled gray or brown on white, lower valve white with 

 gray or brown near umbo; a variant type is orange or lemon color. 

 Nineteen to 23 ribs, narrow ribbing over lateral areas and auricles; 

 fine concentric laminations crossing ribs and interspaces; marginal 

 interlocking of ribs exaggerated. 



This is a lagoon form which is often taken for market. It appears 

 to spawn in shallow water among eel and turtle grass. Young indi- 

 viduals are found attached to grass blades by threads of byssus. 



Genus LYROPErXEN Conrad, 1862 

 Lyropecten iiodosus^" (Linne) PI. 6, fig. 30 



Alt., 95,^Jength, 100 mm. Shell with family characters. Almost 

 equivalve, ears unequal; eight or ten large primary ribs, both sur- 

 face ribs and the wide interspaces uniformly and narrowly ribbed; 

 knoblike nodes developed at more or less regular intervals on the 

 primary ribs — this character is variable; ears and lateral areas 

 finely ribbed; concentric sculpture of fine lamellae, strongest in in- 

 tercostal spaces but sometimes wanting; interior of valves radiately 

 channeled, smooth, reddish colored — deepest near margins. 



Dredged, usually on hard bottom in five to eight fathoms. Young 

 individuals of less than ten millimeters have been taken in five to 

 six fathoms. Not uncommon on the beach after a northwester. 



Family LI3IIDAE 



The living mollusks of the family Limidae possess a delicacy and 

 vivacity which makes them especially attractive subjects for ob- 

 servation. Most of them are red or orange color, with a veil-like, 

 closely plaited mantle which bears numerous extensile, filamentous 

 tentacles which are almost constantly in motion. In an aquarium 

 Lima may be seen to move quite easily over the glass surface by 

 fixing the free extremities of several tentacles, then by contracting 

 them the animal is drawn into a new position. Limas can also swim — 

 as do Pectens — by a rapid flapping of the shell valves; the action is 



3^ Lat., lyra, lyre-shaped ; nodus, knot. 



