ECOLOGY AND BIOLOGY OF THE PACIFIC WALRUS 



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Fig. 99. Remains of molliisks from stomachs of Pacific walruses: (a) siphons of Mya 

 sp.; (b) siphons of Mya truncata; (c) feet of Serripes groenlandicus; and (d) bodies of 

 Neptunea spp. with operculae attached. (Photos by F. H. Fay) 



usual to find only the foot or the siphon of bivalves (Figs. 97^?, 99a,Z7,c) and the 

 soft body of gastropods with the operculum attached (Fig. 99c?). Only the 

 tentacles of cephalopods have been found. 



A few tiny mollusks up to 3 cm in diameter may be swallowed whole 

 {Margarites, Nucula, Cyclocardia, and occasionally Hiatella and Tellina) with 

 shells intact, but I have found only trace amounts of larger molluscan shells. The 

 larger shells were represented by mere fragments, usually from the thin edges of 

 the valves. Most frequently, these were from Serripes groenlandicus, the shell of 

 which is rather fragile. That this scarcity of shells is not due to digestion was 

 indicated by the fact that intact shells of small mollusks, as well as fragments 

 from the valves of S. groenlandicus, were excreted in the feces, having passed 

 through the entire digestive tract with remarkably little alteration. Some minute 

 Nucula, Margarites, and Cyclocardia had both shells and soft parts virtually 

 intact after passage through the tract. 



Arthropoda. —About one-fourth of the walrus stomachs that I examined 

 contained one or more crustaceans; in several instances, these were among the 



