128 BULLETIN UNITED STATES GEOLOGICAL SUEVEY. lYol.YJ. 



produced behind by cartilage, or rather tipped by that material, while 

 the articulation at the anterior extremity of these confluent bones is 

 hidden from view in the superior aspect of the arch by the giosso- and 

 cerato-hyals ; and, as is common, the inferior lip that thebasi-hyal lends 

 to this joint is the longer, and protrudes forward. 



The hypo- and cerato-branchial elements of the thyro-hyals are very 

 long, slender, up-curved little bones, produced posteriorly, as the uro- 

 hyal, by cartilaginous tips. 



The shaftlets of these delicate elements are slightly flattened from 

 above downwards, as are the articular heads. The free extremities have 

 a tendency to curve inwards a little, or towards the median plane, as 

 well as upwards. 



The lower mandible — (Plate lY, Figs. 22 and 29). — EremopMla is an- 

 other example exhibiting the non-approximation of the tomal edges of 

 the mandibles in the dry skull, this feature being more often absent 

 among Grallatores and many of the Natatores, where these edges come 

 in contact with almost an equal amount of exactness as where the bill 

 is armed with its horny theca. 



The lower mandible of the Horned Lark seems to be, in point of struct- 

 ure, composed almost entirely of compact tissue, and, owing in addition 

 to the thorough coalescence of its primary elements, a very firm and 

 strong bone. Sutural traces, the indicators of the boundaries of pris- 

 tine segments, have entirely' disappeared, and no one would ever suspect, 

 in examining it, the presence of nine original parts, were he not familiar 

 with avian osteology or had the opportunity of dissecting the young. 

 The inferior surfaces of the articular ends are on a level with the major 

 part of the under rim of the rami, but they are well below the coronoidal 

 elevations on either side. They present superiorly the usual undulatory 

 surface to meet and articulate with the condyles of the tympanies. 

 Below ai^pears a longitudinal ridge, due to the extension upon that side 

 of the ramal edges. A knob-like process projects behind, and the true 

 articular processes are sharp and rather long. They are directed inwards, 

 upwards, and then forwards, ha^ang the usual pneumatic foramen above 

 and near their pointed extremities. The su^Derior margin of the inferior 

 maxilla starts at once from each articular surface, to rise by a moder- 

 ate angle to the representative coronoids, a distance of 4 millimetres; 

 it then falls gradually to the rounded and anterior termination of the 

 bone. It exhibits about its middle, on each side, a long but very low 

 convexity, the corresponding shallow concavities being between them 

 and the coronoidal elevations. The "coronoids" are marked by deep 

 groovelets with raised borders, that extend forwards and downwards as 

 far as the interangular vacuity. 



The inferior boundary of the bone, as already stated, rises on each 

 side in the inferior articular surfaces, to ascend first for two-thirds of 

 its extent on each ramus, then to fall at about an equal angle, to sweep 

 round and form the anterior and curved termination in the dentary ele_ 



