374 



DR. E. W. SHUFELDt's MORPHOLOGICAL 



caudal, tlie semitendinosus, and the accessory semitendinosus 

 muscles from the group at the thigh ; in other words, their formula 

 is A. 



This from a physiological point of view would naturally be 

 looked for, as no members of these groups use their limbs for loco- 

 motory purposes ; and consequently these special muscles have 

 long since been missing, or perhaps iu neither of them have they 

 ever been present. But to this matter I shall refer further on. 



Coming next to the 'plantar tendons, I find the arrangement in 

 the Swifts at hand the same as described by Garrod for Cypselus 

 aJjnmts fColl. Scient. Mem. p. 294), and as that has already 

 been made clear to us, I need not quote it here ; but after having 

 carefully prepared the foot of a specimen of Trocliilus platycerciis, 

 and bringing the limb under the lens of a powerful objective, 

 which increased the size of this Humming-bird's foot to that of a 

 Crow, I was enabled at once to discover that the arrangement of 

 the plantar tendons in these birds is very different from what 

 obtains in the Cypseli ; in other words, in TrocJiilus these tendons 

 are disposed very much as we find them in the Passeres, where the 

 tendon of the flexor longiis Jiallucis is distinct from that of the 

 flexor iperforans digitorum. It is just possible that in Humming- 

 birds a slight vinculum may connect the two, and although I 

 could not quite satisfactorily demonstrate this minor point, yet 

 I am inclined to think that such a vinculum is present. 



I found the sciatic artery the main artery of the leg in both 

 Cypseli and Trochili, but that is the usual arrangement for 

 nearly all birds, which weakens its importance as a distinctive 

 character. 



As to the skeleton of this limb in these birds I have already 

 contributed some work (P. Z. S. 1885, pp. 909-913), and little 

 or nothing need be added here. Suffice it to say that morpho- 

 logically the constitution of the pelvic limb, so far as its skeleton 

 is concerned, is radically diff"erent in Cypseli and Trochili. A 

 few points will be sufficient to convince any one of this fact, 

 for in TrocJiilus, for instance, we have a large patella present, a 

 bone entirely missing in Micropus ; in Trocliilus we have the 

 hypotarsial process of the tarso -metatarsus both pierced and 

 grooved for the passage of the tendons, whereas in Micropus it 

 simply exhibits one deep groove for that purpose ; finally, the foot 

 in each case is widely difi*ercnt, for in Trocliilus tlie joints of pes 



