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Show 1889.] MR. W. K. PARKER ON STEATORNIS CARIPENSIS. 183 the distal tarsal over the 4th metatarsal; it is 1 millim. across, 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 the tibia. It is much like the same part in the " Ornitho-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 1st 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-metatarsal 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:-1st, 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, in a 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 toyether as the 4th or penultimate ; this is 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 Professor Huxley (Proc. Zool. Soc. 1868, p. 311) has constituted for the Hoatzin (Opisthocomus cristatus). If it were allowable, the term " Heteromorphae " should be kept for all those birds that cannot be classified : that refuse to be put into any of our normal groups. W e 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, cannot 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 13* |
