4r)4 UR. R. BROOM OX THE 



continued backwards from the palatine. A long slender out- 

 ward process extends underneath the alisphenoid and in close 

 relation to it. Downwards and backwards there passes a strong 

 hooked process which supports the soft palate. The general 

 shape will be readily understood from the restored figure 

 (text-fig. 2). 



External to the pterygoid and posterior to it is seen the large 

 bopy ring of the tympanic. It forms about § of a circle. 

 Lying between it and Meckel's cartilage is seen the piearticular 

 or " goniale " of Gaupp ; and immediately internal to the pre- 

 articular is a slender splint of bone which has not, so far as 

 I am aware, been previously observed in mammals. It may 

 i-epresent the surangulai- of the reptilian jaw. 



External to the tympanic is seen tlie developing squamosal. 

 It curves round the auditory region, and in the figure is seen 

 extremely foreshortened. In the slightly older skull the 

 squamosal passes much further downwards and inwards and 

 protects the whole of the posterioi- tympanic region Avhich at 

 tliis stage is exposed. 



Behind the auditor}^ capsule is seen the developing tabular; 

 it is in close association with the anterior border of the supra- 

 occipital. 



In the figvu^e given the only other membi'ane-bone seen is the 

 frontal, a considerable part of whose lowei- border is shown. 

 A large foramen shown is occupied by a venous sinus. 



Cli.ondrocranium and cartilage-hones of the iieAfly-horn 

 Ohiysochloris hottentota. 



Text-figure 3 shows a reconstruction of the chondrocranium, 

 almost all the meml)rane-bones having been removed. The most 

 striking general features are the great size of the occipital and 

 auditory regions, the very small size of the orbitosphenoid, and 

 the well-developed condition of the nasal capsules. 



The internal structure of the nasal capsule is to some extent 

 revealed in the figures of sections given. In the reconstructed 

 fio'ure the most intei'esting feature shown is the primitive struc- 

 ture of Jacobson's cartilage. It will be observed that there is, 

 as in marsupials and a few lowly-organised Eutherians, an outer 

 bar which is, however, not quite completely formed. There is a 

 small posterior nasal-fioor cartilapge. 



The oi'bitosphenoid is unusually sma.ll and does not extend far 

 backwards as it does in marsupials and primitive Eutherians. 

 It has a. foramen rotundum for the rudimentai'V optic nerve. 



On the base of the posterior part of the nasal capsule is a 

 large membrane-bone of doubtful significance. Text-fig. 3 shows 

 the appearance of the bone as viewed from below after the 

 removal of the vomer, palatine, pterj^goid, and alisphenoid. 

 In the figui'es of sections given (Pis. I., II., figs. 6-8) the 

 relations of the bone to the nasal capsule, to the orbitosphenoid. 



