No.5.] SHUFELDT ON THE OSTEOLOGY OF EREMOPIIILA. 127 



The longitudinal sinus is best seen along the superior and median 

 crest, just before it arrives at the olfactory foramen. The middle fossa 

 for the accommodation of the cerebellum is distinctly nmrked by long 

 transverse concavities, admitting the rugai upon the lobe in question 

 when the brain is in situ. With regard to the structure of this bird's 

 cranium, we may say that it is largely cancellated, the intermaxillary 

 and petrosal approaching nearest the compact variety of bone; this fact 

 lends to this part of the skeleton a great lightness, and well-prepared 

 skulls of this Lark are very pretty objects. 



The most remarkable feature to be observed, however, is the great 

 amount of separation between the tables of the vault of the brain cavity, 

 being fully a millimetre, and in some localities more, the interspace being 

 filled in by quite an open diploic tissue. This condition we well know 

 to be a striking feature in the anatomy of the Strigidcc, but here is a 

 bird that has the same arrangement as well marked, we believe, for its 

 size, as any Owl in the North American fauna. The outline of the base 

 of the cranium in Mremophila approaches the sector of a circle, a figure 

 more or less true in all birds, and here, as in most others, the greatest 

 departure from that figure being a too great convexity of the subtending 

 arc. The length of the radius represented by the middle line is 3.2 centi- 

 metres, the iutertympanic chord, including the bones, being 1.4 centi- 

 metres. We will only mention here, in regard to the free osseous ele- 

 ments of the sense capsules, that the sclerotals retain their usual form 

 and arrangement, numbering in each eye Irom thirteen to fifteen. The 

 attachment among them is rather firm, remaining as shown in PL IT? 

 Fig. 41, after a considerable amount of maceration. The ossicula auditus 

 are also present, but a lens of some power is required to study their form 

 and arrangement. 



The liyoid arc/i— (PI. IV, Fig. 37, seen from below).— This, the haemal 

 arch of the parietal vertebra, in no way deviates in this little Lark from 

 the usual ornithic characters possessed by it among living birds, in being 

 freely suspended beneath the cranium and acted upon by certain mus- 

 cles. The glosso- and cerato-hyals seem to be confluent, and the bone 

 thus formed consists in two narrow little affairs, that for their anterior 

 two-thirds run alongside of each other with a greater or less intimacy, 

 to have their tips slightly diverge anteriorly. Posteriorly the ends have 

 a still greater amount of divergence, and at the junction of the middle 

 and posterior thirds there is a transverse bony bridge, that bears the 

 facette for articulation with the basi-hyal behind. Scarcely any antero- 

 posterior curvature exists. The posterior tips overhang the articula- 

 tion of the thyro-hyals with the confluent basi- and uro-hyal. These 

 latter have an expansion to accommodate the articulation referred to, 

 bearing on either side small, elliptical, articular surfaces, looking 

 backwards and outwards for the heads of the hypo- branchial elements 

 of the thyro-hyals. 



The bone is subcompressed from above downwards, the uro-hyal being 



