FOSSIL AIS'D EECENT LAGOMORPHA. 495 



constantly after the foixrth month *. Leboucq considers this cartilaginous nodule of the 

 human foetus the homologue of the ossicle in Hi/ lobnt.es; both are parts of the 

 pisiform, the pisiform of human anatomy being, in his opinion, but the distal epiphysis 

 of the complete pisiform f . In a later paper the cartilaginous nodule is homologized 

 with the OS trigonum (tarsi) : " je crois done pouvoir considerer ce nodule et I'os trigonum 

 comme homologues " %, whence it would follow that the ossicle of Hylobates is equally the 

 homologue of the trigonum. 



The ephemeral cartilage of the human embryo has since been discovered in an ossified 

 condition in a carpus of an adult, and received the name triqueti'um secundariuni §. 

 Both this cartilage in the foetus and the triquetrum secundarium occupy a more radiad 

 position than the ossicle of the Gibbon, wherefore it would appear that tliey are not, 

 after all, the homologues of the latter, and this is proved to be the case by the discovery 

 by Kohlbrugge of tvo accessory ossicles in the Gibbon. In three specimens of the three 

 species Ilijlohates leuciscn^, H. (((/Uis, and II. Millleri, an ossicle is situated between the 

 styloid process of the ulna, the pisiform, and the ulnare. It rests on the processus 

 styloideus and articulates with it and the ulnare. The pisiform joins the carpus 

 at the jioint of junction between the ossicle and the ulnare. Kohlbriigge recalls the 

 description of Daubenton, in whose honour the ossicle is named {ossiculum Dauientonu) ; 

 and he adds that Camper had seen it in the Inuus ||. In the carpus of a Hylohales 

 syndactyhts the following condition is described :— " Sitiiated between the radius aad the 

 ulnare is an ossicle, which is joined to the radius and to the ossiculum Daubentouii by a 

 fibrous ligament ; between both is cartilaginous tissue." The ossicle which, to all 

 appearance, is that described by Camper in the Mandrill — and which has hence received 

 the name ossiculum Camper ii — was present in both hands of the Gibbon ; in the left 

 manus the ossiculum Daubentonii was reduced to a small osseous nucleus ^. From its 

 position, the ossiculum Camperii corresponds to the cartilaginous nodule discovered by 

 Leboucq in the human foetus, and is therefore the homologue of the triquetrum 

 secundarium (triangulare) of Man **. There can be no doubt that the ossiculum 

 Daubentonii is the element Avhich Leboucq has described in an adult II. leuciscus, since 

 they occupy the same position. In Leboucq's figure — doi-sal aspect of the carjnis — the 

 pisiform (jj.) has been removed backward, in order to bring it into evidence ff. 



* Op. dt. p. 81, pi. iii. fig. 17. t Op. rlt. p. 83. 



i H. Leboucq, " Sur la Morphologic du carpe et du tarse," Aiiat. Anz. i. p. 20 (]88(i). 



§ Pfitzner, " Eemerkung-en zum Aufbaii des monschl. Carpus," Verb. Anat. Ges, 7. Vers, in Gijttingen 1893 

 (Ergiinzungsbeft Anat. Anz. viii. p. 191 (1893).— See also Morph. Arb. iv. p. 508 (189.5). 



[| J. H. F. Koblbriigge, " Versueb ciner Anatomie d. Genus ffi/lohates" (M. Weber, Zool. Ergebn. eiuer Eeise iu 

 ISfiederlandiscb Ost-Indien, i. pp. 338, 339, pi. xvii. fig. 9 (1890-91). 



If Op. cit. p. 339, pi. xvii. fig. 10. 



** Tbe ossiculum Camperii (triquetrum secundarium, triangulare) or. as Thilenius terms it, os intermedium ante- 

 hrachii, has been found in Homo, Bi/Iobates, and Ininis, as mentioned in the test, and, by Pfitzner, in a carpus of 

 PliascoJomys. Pfitzner's specimen is figured and described by Thilenius (Morph. Arb. v. p. 9, pi. i. fig. 12 (180.5)). 

 I find -what I take to be the same bone in Lemurs, Insectivora, and Piodentia, -nbereon more will be said in another 

 place. (See P. Z. S. London, 1899, pp. 428-437.) 



tt Oi'. cit. p. 101 (explan. of fig. 28). 



