The upper mandible is
furnished on each side (in the specimen examined by me) with a row or comb
formed of 188 thin, elastic lamellae, obliquely bevelled so as to be
pointed, and placed transversely to the longer axis of the mouth. They
arise from the palate, and are attached by flexible membrane to the sides
of the mandible. Those standing towards the middle are the longest, being
about one-third of an inch in length, and they project fourteen one-
hundredths of an inch beneath the edge. At their bases there is a short
subsidiary row of obliquely transverse lamellae. In these several respects
they resemble the plates of baleen in the mouth of a whale. But towards
the extremity of the beak they differ much, as they project inward, instead
of straight downward. The entire head of the shoveller, though
incomparably less bulky, is about one-eighteenth of the length of the head
of a moderately large Balaenoptera rostrata, in which species the baleen is
only nine inches long; so that if we were to make the head of the shoveller
as long as that of the Balaenoptera, the lamellae would be six inches in
length, that is, two-thirds of the length of the baleen in this species of
whale. The lower mandible of the shoveller-duck is furnished with lamellae
of equal length with these above, but finer; and in being thus furnished it
differs conspicuously from the lower jaw of a whale, which is destitute of
baleen.
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