374 
DU. E. W. SHUFELDt’s MORPHOLOGICAL 
caudal, the 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 he 
looked for, as no members of these groups use their limbs for loco- 
rnotory purposes; and consequently these special muscles have 
long since been missing, or perhaps in 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 
alpinus (Doll. 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 platycercus , 
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 Trocliilus these tendons 
are disposed very much as we find them in the Passeres, where the 
tendon of the flexor longus hallucis is distinct from that of the 
flexor perf or ans 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 different in Cypseli and Trochili. A 
few points will be sufficient to convince any one of this fact, 
for in Trocliilus , for instance, we have a large patella present, a 
bone entirely missing in Micropus ; in Trocliilus we have the 
hypotai’sial 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 different, for in Trocliilus the joints of pes 
