General Notes. 



437 



it maybe conveniently and appropriately called bv this shorter name, 

 without prejudice to the question, which of the four human dorsossei it 

 represents — apparently the tertius or qtiarlus. 



12. 'Abductor indicis.' A dorsosseus apparently secundiis or tertius. 



13, 14. ' Flexor ' and ' adductor pollicis. Two small thumb muscles situ- 

 ated upon the back of the manus, of uncertain systematic position. One 

 of them may be really a dorsosseus; but that depends, as before, upon to 

 which digit of the pentadactyl hand the thumb of a bird's tridaclyl hand 

 corresponds. One of these muscles is displayed in my Carus figure, ' t,y 

 flexor brevis pollicis.' 



15. 'Musculus interosseus palmaris.' This muscle, which has been 

 specially drawn upon in the controversy elsewhere alluded to,* is situate 

 on the 'internal' (that is, the palmar) aspectof the manus; it is therefore one 

 of the three palmossei o( C & S., but which one, remains to be decided. 



16,17. 'Extensor' and 'adductor pollicis brevis.' Two 'polIicaP 

 muscles, to which the same remarks apply as to Nos. 13 and 14. It would 

 seem that a bird's thumb, aside from its ' long' muscle which comes from 

 the tbrearm. is exclusively actuated by four 'short' muscles, which flex, 

 extend, abduct, and adduct it. Such regular musculation should not 

 be difficult to homologize, but we must first settle the status of the digit 

 itself. If a bird's hand be no exception to the probably invariable rule in 

 mammals, that, when digits are reduced in number from five, the reduction 

 is from eac/t side alternately, so that digits I and V are the missing ones 

 in a tridigitate member, then obviously, the three digits of a bird are II. 

 Ill and IV corresponding to our index, middle and ring fingers. But if, in 

 a bird, two digits have gone from the ulnar side, then the bird's three digits 

 arc I, II, III, corresponding to our thumb, index and middle fingers. I 

 think that very likely a careful dissection of the two main nervous trunks 

 of the forearm would throw a light upon the question which jierhaiis the 

 examination of the embryonic carpus and metacarpus has not hitherto 

 aft'orded. 



18. 'Flexor liigiti tertii.' Apparently one of the hypolhenar subgroup 

 of C. and S., but possibly a palmosseus : its identification depends ujion 

 that of the digit in question. — Elliott Coue.s, Washingtoti, D. C. 



*This number of The .Auk, p. 418. 



