BY WILLIAM A. nASWELL, M.A., B.SC. 309 



insessorial birds, and the nocturnal Raptores ; it distinguishes 

 these, however, from the wading and swimming orders, in which 

 the bellies of these two muscles are separable from one another. 



b. — Muscles of the Posterior Extremity. 



1 . — The gluteus externus is absent. This seems to be characteristic, 

 besides the present group and its allies, of the Parrots, Kingfishers 

 Cuckoos, and the Passerines. 



2. — The adductor brevis, adductor longus, semimembranosus, semi- 

 tendinosus and accessory semitendinosus are all present. The 

 significance of these muscles has been pointed out by Mr. A. H. 

 Garrod.* 



3. — The Ambiens (Pectineus) and the flexor per -for -atus digitorum 

 have a peculiar and characteristic arrangement in this family. In 

 several genera of Columlidce as Mr. Garrod has pointed outf the 

 ambiens is altogether absent : where it is present, as occurs in the 

 majority of genera, its tendon on reaching the back of the leg, 

 in place of breaking up and losing itself among the fleshy fibres 

 of the superficial flexors, maintains its consistency, and joins a 

 strong tendon which, arising from the fibula, passes into a small 

 muscular fasciculus — the accessory or fibular head of the flexor 

 perforatus secundus tertii digiti. Such a definite relation of the 

 distal tendon of the ambiens to one special muscle is rare, if not 

 exclusively characteristic of the present group. In certain Anseres 

 ( Erismatura, CasarcaJ however, an arrangement which, though 

 more complex, has a certain analogy with the above, is to be 

 observed : here the tendon of the ambiens after becoming connected 

 by a tendinous band with the head of the fibula, divides into three 

 parts, each of which developes a little muscular slip becoming 

 connected, one with the flexor perforatus primus secundi digiti, the 



*" On certain Muscles of the Thigh in Birds and their value in Classification," 



P Z S , 1873, pp. 626—644, and 1874, pp. 111—123. 

 f " On some points in the Anatomy of the Columbse," P.Z.S., 1874, pp. 249 



—259. 



