The Duck-bill Shells and Lantern Shells 



shaped process in each valve, usually a triangular ossicle between ; 

 siphons separate, long, slender. About a dozen species distrib- 

 uted on coasts of the western hemisphere. 



The Silvery Lantern Shell (P. planiscula, Sby.) has a 

 smooth, delicate white shell with a silvery lining. Its hinge is 

 near the posterior end of the oblong valves wliich taper toward 

 the rounded anterior end. Under each beak is a spoon-shaped, 

 forward-turning internal hinge tooth. The left valve is flat, 

 the right bulged. These are such fragile shells that waves which 

 cast one on the beach usually ruin the shell as a specimen 

 for the cabinet. Length, i to 2 inches. 



Habitat. — Southern California. 



The Paper Lantern Shell (P. -papyracea, Say) is fragile, 

 white and pearly, like its prototype on the west coast. It is 

 rounded in outline, almost as broad as long, but tapering somewhat 

 to the posterior end, the outline falling abruptly from the sub-cen- 

 tral beak. The lines of growth and the groove from the beak are 

 well marked. The surface is covered with minute wrinkles. 

 The tooth is long, narrow, with an accessory process at the base. 

 Length, f inch. 



Habitat. — Gulf of Mexico, Atlantic Coast. (Rare.) 



Lea's Lantern Shell {P. Leana, Conr.) has a broad, regu- 

 larly rounded outline, which slants away from the beak to the 

 slightly narrow posterior end. 1 1 is fragile and white, with a diago- 

 nal ridge from the beak. Surface wrinkled, with an overhanging 

 yellow, shining epidermis. Each hinge has a spoon-shaped inter- 

 nal process set almost horizontally and resting on an oblique 

 rib. Length, ij inches. 



Habitat. — Northern Atlantic coast. 



The Round Lantern Shell (P. discus, Strns.) is another 

 of the fine species credited to the local collectors at Long Beach, 

 Cal. For a time specimens were very rare. The valves are 

 almost circular. The hinge line is approximately straight, and 

 there is a truncated snout at the posterior dorsal corner. The 

 thin, white valves are concentrically grooved. Length, 2 inches. 



Habitat. — San Pedro, Cal. 



Genus LYONSIA, Turt. 



Shell sub-triangular, valves unequal, thin; hinge with narrow 

 ledge in each valve containing ossicle and ligament; siphons short, 



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