The Rock- borers 



margins a horn-like tooth and a socket on each valve; ligament 

 external, conspicuous; siphons separate at tips. 



Few species, including some clams of unusual size, widely 

 distributed, chiefly in cold seas. 



f The Norwegian Panopaea (P. Norwegica, Spengl., Glyci- 

 meris arcticus. Lam.) is found off New England coasts and dis- 

 tributed by way of Arctic seas to Norway and Asia. Its trape- 

 zoid shell is thick, and each valve is divided into equal triangular 

 thirds by two raised ribs that diverge from the hinge. The 

 squared posterior end is broad, but scarcely more so than the 

 great siphon tube that emerges, wearing its tough, dark skin in 

 wrinkles until it is stretched at full length. In New England 

 a good average of these shells is three inches long. In Norway 

 they grow somewhat larger. 



The Giant Panopaea (P. generosa, Gld.) lacks the posterior 

 diverging ridge on the shell. It is the largest bivalve of the west 

 coast. Six inches, the average length, is often greatly exceeded. 

 The valves are flat, almost right-angled behind, rounded in front; 

 distinct concentric growth lines mark the dull white exterior; the 

 lining is pearly. The foot is small. The siphons are large and 

 united, their chief protection a thick, wrinkled skin. The tube 

 reaches a full yard in length with a thickness somewhat exceeding 

 that of a stout broom handle. When disturbed the mollusk 

 throws out a powerful jet of water, and retires to a depth dis- 

 couraging to the collector. 



"A truly noble bivalve!" is the characterisation applied by 

 a conchologist who dug one out of the mud with the aid of two 

 friends, one of whom had the arduous task of hanging on with a 

 death grip to the great siphon, while he adjured his colleagues to 

 dig for their lives, as his grip was likely to give out. This speci- 

 men weighed sixteen pounds. Dr. Stearns says : "The meat, when 

 parboiled and fried in batter, is as tender as a humming bird's 

 eye." The Indian name for this favourite clam is "Geoduck." 

 It is found in Puget Sound. 



Aldrovand's Panopaea (P. Aldrovandi, Lam.) of the Medi- 

 terranean IS the giant of the genus. It is broad and deep, short 

 and obliquely truncated in front. The lines of growth are uni- 

 form and distinct. Length, lo inches. 



The Attenuated Panopaea {P. attenuata, Sby.) from Port 

 Natal, South Africa, long and narrow, is another giant. 



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