1889.] MR. W. K. PARKER ON STEATORNIS CARIPENSIS. 183 



the distal tarsal over the 4th metatarsal ; it is 1 millina. across, and 

 runs downwards 2-5 millim. The whole tarso-metatarsus is less 

 than half the length of the lemur and Httle 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 Cijpseline 

 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: — 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 together 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 tlie only Neotropical type that 

 asks to be put into a se|)arate suborder, such as that which Pro- 

 fessor Huxley (Proc. Zool. Soc. 18G8, p. 31 1) has constituted for the 

 Hoatzin {Oj^nstkocomus cristatus). 



If it were allowable, the term " Heteromorphse " should he 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 

 AduUam " 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 iu 

 those types that are evidently Archaic, we meet viiihsome 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 co?25e?T«;^2j;e and almost extinct 

 family — extinct but for it, the Oil-bird has some characters that 



13* 



