Internal Structure of the Bearded Titmuuse. 321 



Professor IMacgillivray has clearly shown that the alimentary 

 system has a structure of quite an opposite nature to that of 

 these birds. 



I shall now endeavour to show that the sternum indicates a 

 greater affinity with the FrinfjiUidce than with the Paridce ; but 

 I must premise that this part, although of great importance in 

 assisting in the determination of families, is much less service- 

 able in distinguishing between genera, and this renders it diffi- 

 cult, if not impossible, to say, by this means, to what genus the 

 Calamophilus is most nearly allied. In a family of birds, like 

 the FringilUdce, which is not characterized by any very strongly 

 marked peculiarities common to them all*, it may readily be 

 conceived that the moditications of the sternum, however constant 

 in the different groups, will be extremely difficult to define with- 

 out the help of figures. In the present instance I should utterly 

 fail to convey any intelligible idea by means of a detailed 

 description, which would become one of measurement of parts 

 merely, and this, in small objects, is often unsatisfactory. It will 

 be better therefore to choose the sternum of some common species 

 with which to compare that of the Calamophilus, and broadly 

 state how they resemble each other. The sternum of the Com- 

 mon Sparrow resembles that of the Calamophilus, 1st, in the 

 relative length of the furculum and coracoids with that of the 

 sternum itself; 2nd, in the general outline of the latter, and in 

 the shape of the keel ; 3rd, in the extent and shape of the notches 

 of the hinder margin, and (especially) the shape of the process 

 which is separated from the body of the bone on either side by 

 the notches. 



The following genera, which I have specially examined in these 

 investigations, appear to me to hold relationship to each other 

 in the following manner, their several adaptations being the chief 

 difference between them :— 



LoxiA. Fringillid<£ with mandibles modified for the purpose of 

 extracting the seeds of Coniferaj. 



* Take a Hawfinch, Crossbill, Bullfinch, Goldfinch, Rc(l))olc, and Spar- 

 row, and remove that which adapts each to its y)ceuliar re'i/ime; and what 

 remains will he fonnd to be very similar in all, and possessed of no striking 

 external characters. 



