chap, xiii.] DIGITS : BIRDS. 393 



Two extra digits are said to be not uncommon in the Dorking but I have 

 myself seen only one case. A foot of this kind is figured by Cowper 1 , 

 and in it the appearance is as of an extra digit of three joints (1 all 

 phalanges) arising internally and proximally to the hallucal metatarsal, 

 which already bears two small and sub-equal digits. In the case seen 

 by myself there was one large internal digit with three phalanges sepa- 

 rately articulating with the tarso-metatarsus, and the hallucal metatarsus 

 bore a digit divided peripherally, bearing two nails related as images. 

 Here therefore there was a double hallux, and internal to it a separate 

 digit. 

 598. The evidence regarding extra digits in other positions, though small 

 in amount, is of importance as a light on the morphology of these repeti- 

 tions of digits. We have seen that the ordinary extra digit is, with 

 the hallux, borne on the hallucal metatarsal. In one of Howes' cases 

 (I. c. figs. 2 and 3) this metatarsal instead of simply articulating with 

 the shank of the tarso-metatarsal ivas continued up to articulate also 

 with the tibio-tarsus. From this state the condition in which a separate 

 digit (or digits) articulates with the tibio-tarsus only is not far removed. 

 Of this condition I know no detailed account in the Dorking, though it 

 is referred to by Lewis Wright 2 , but I have met with the following 

 cases in other birds. 



i99. Aquila chrysaetos (Golden Eagle) : having two extra toes borne by right 

 metatarsus [left foot is not described]. The two extra toes attached to upper part 

 of the back of the metatarsus. Each bears a full-sized claw which was curved 

 backwards and upwards. One of the toes bore six scutella on the morphologically 

 upper surface and four on the plantar surface. The other toe, which was more 

 completely united to the metatarsus along its whole length, bore only a single 

 scutellum on the plantar surface. The rest of the foot was normal. Jackel, A. J., 

 Zool. Gart., xv. 1874, p. Ul,fig. 



00. Pheasant: right foot bearing a thin and deformed digit articulating internally 

 with the distal end of tibio-tarsus. Hallux normal. Left not seen. Specimen 

 received from Mr W. B. Tegetmeier. 



01. Pheasant: each leg bears a large extra digit of irregular form attached to the 

 middle of anterior surface of tibio-tarsus. The two legs almost exactly alike, but in 

 one the digit is firmly and in the other loosely attached to tibio-tarsus. Specimen 

 kindly sent by Mr Tegetmeier. 



02. Buteo latissimus <r , having extra digit on right leg, the toe was well formed, 

 with two phalanges, bearing perfectly formed claw, loosely attached internally 

 to tibio-tarsus just above articulation with tarso-metatarsus. Coale, H. K., Auk, 

 1887, iv. p. 331, fig. [Cp. No. 593.] 



03. Turkey having two imperfectly separate digits ['? images] attached to process of 

 tibio-tarsus. Two cases differing in degree: hallux normal. Ercolani, Mem. Ac. 

 Bologna, Ser. iv. in. PI. m. figs. 2 and 3. 



04. Pheasant: somewhat similar case, in which two such digits were similarly 

 placed, but one was large and the other small. Ibid., fig. 4. 



05. Larus leucopterus. For the following case I am indebted to Professor B. 

 KiDGWAT, Curator of the Department of Birds, in the United States National 



1 Cowper, J., Journ. Anat. Phys., xxm. p. 249. 



2 "Perhaps tbe most difficult point in judging Dorkings, however, is to watch 



against malformations of the feet which have been fraudulently removed ; for 



the abnormal structure of the Dorking foot is very apt to run into still more abnor- 

 mal forms, which disqualify otherwise fine birds for the show-pen. Birds are not 

 unfrequently produced which possess three back toes, or have an extra toe high up 

 the leg ; or, in the case of the cock, with supernumerary spurs, which have been 



known to grow in every possible direction We have on two occasions seen 



prizes awarded to birds which shewed unquestionable traces of such amputation...." 

 The Illustrated Book of Poultry, 1886, p. 331. 



