SEC. Ill EXTERIOR PARTS OF BIRDS 151 



Stercorarius). The tumid nasal skin of pigeons is sometimes called 

 a cere ; but the term had better be restricted to the birds first 

 above named. The under mandible probably never presents soften- 

 ing, except as a part of general skinniness of the bill ; it may have 

 a nail at the end. (J.) The covering is either entire or pieced. In 

 most birds it is entire ; that is, the sheath of either mandible may 

 be pulled off vrhole, like the finger of a glove. It is, however, in 

 many birds divided into parts, by various lines of slight connection, 

 and then comes off in pieces ; as is the case with some water birds, 

 particularly petrels, where the divisions are regular, and the pieces 

 have received distinctive names. Many auks {Alcidm) have the 

 covering of the bill in particular pieces, and it is an extra- 

 ordinary fact that such parts are of a secondary sexual character, 

 being assumed at the breeding season and afterwards moulted like 

 feathers. Such condition of the sheath of the beak, or of special 

 developments of the sheath, is called caducous or deciduous. The 

 entire covering of both jaws together is called rhamphothcca (Gr. 

 pa.jx.'^o'i, hramphos, beak ; Or/Kr], theke, a sheath) ; of the upper alone, 

 rhinotheca (Gr. pts, hris, the nose) ; of the under, gnathotheca (Gr. 

 yvado-s, gnathos, jaw); but these terms are not much used, (c.) 

 The covering is otherwise variously marked ; sometimes so strongly 

 that similar features are impressed upon the bones themselves be- 

 neath. The most frequent marks are various ridges (Lat. pi. carince, 

 keels) of all lengths and degrees of expression, straight or curved, 

 vertical, oblique, horizontal, lengthwise, or transverse; a bill so 

 marked is said to be striate (Lat. stria, a streak) or carinaie ; when 

 numerous and irregular, they are called rugce (Lat. ruga, a wrinkle) 

 and the bill is said to be corrugated or rugose. When the elevations 

 are in points or spots instead of lines, they are called puncta (Lat. 

 punctum, a point) ; a bill so furnished is punctate, but the last word 

 is oftener employed to designate the presence of little pits or de- 

 pressions, as in the dried bill of a snipe towards the end. Larger 

 softish, irregular knobs or elevations pass under the general name 

 of warts or papillcB, and a bill so marked is papillose; when the 

 processes are very large and soft, the bill is^ said to be carunculafe 

 (Lat. caro, flesh, diminutive carunculus, little bit of flesh). Various 

 linear depressions, often but not always associated with carinse, are 

 grooves or sulci (Lat. sulcus, a furrow), and the bill is then called 

 sulcate. Sulci, like carinse, are of all shapes, sizes, and positions ; 

 when very large and definite, they are sometimes called canalicuU, 

 or channels. The various knobs, " horns," and large special features 

 of the bill cannot be here particularised. Any of the foregoing 

 features may occur on both mandibles, and they are exclusive of 

 that special mark of the upper (the nasal fosscc) in which the 

 nostrils open, and which is considered below. We have still to 



