1889.] MR. W. K. PARKER ON STEATORNIS CARIPENSIS, 183 
the distal tarsal over the 4th metatarsal; it is 1 millim. across, and 
runs downwards 2°5 millim. The whole tarso-metatarsus is less 
than half the length of the femur and little more than one third the 
length of thetibia. It is much like the same part in the “ Oruitho- 
scelida,”’ except for the fusion of its elements. The breadth, below, 
across the condyles for the four digits is 11 millim. nearly, two thirds 
as much as its whole length, namely 17°5 millim. The condyle for 
the lst is 4 millim. higher up than that for the 3rd digit. The 
whole series of metatarsals in the distal part of the shank are 
curiously twisted backwards, from without inwards, so that all the 
condyles lie nearly on the same oblique plane; this is a very Cypseline 
state of things. The breadth, above, of the small tarso-meta- 
tarsal is 6°5 millim., in the middle 4 millim. The condyles are all 
grooved, the groove is deepest on that for the 3rd digit. 
The length of the digits (Plate XIX. figs. 4, 5, dy. 1-4) is as 
follows :—I1st, 17 millim.; 2nd, 30 millim.; 3rd, 36 millim.; and 
4th, 33 millim. The proximal phalanges increase in length and 
thickness, gently but sensibly, from without inwards, ina very regular 
manner. The proximal phalanx is shorter than the penultimate in 
the 3rd and 4th digits; the two are equal in the 2nd; in the 4th 
the 2nd and 3rd phalanges are not so long together as the 4th or 
penultimate ; thisis a rare structure. The claw-joints are strong and 
well-curved. 
VII. Summary. 
The Guacharo (Steatornis) is not the only Neotropical type that 
asks to be put into a separate suborder, such as that which Pro- 
fessor Huxley (Proc. Zool. Soc. 1868, p. 311) has constituted for the 
Hoatzin (Opisthocomus cristatus). 
If it were allowable, the term “ Heteromorphz ” should be kept 
for all those birds that cannot be classified: that refuse to be put 
into any of our normal groups. We should then have a ‘ Cave of 
Adullam” for all those waifs and strays from the old Avifauna ; 
birds that, like the Flamingo, the Palamedea, and the types just 
mentioned, canuot be bound up with the other bundles, because the 
cords that keep the normal birds into such a neat ornithological order 
will not tie when bound round these abnormal forms, even if carried 
round them nine times! 
When, as in Steatornis, only one species is still living of an 
evidently isolated type, the inference is at once made that here, if 
anywhere, we have an Archaic kind of bird. I think that I have made 
it clear in the foregoing description that this is really the case in 
this instance. 
There is one difficulty in this kind of research, namely, that in 
those types that are evidently Archaic, we meet with some characters 
that are seen at once to be the result of the very last or newest 
specialization that this type of skeleton has undergone. 
Of course Steatornis has had as much time to do this in as any 
other bird ; but, whilst belonging to a conservative and almost extinct 
family—extinct but for it, the Oil-bird has some characters that 
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