184 m report — 1846. 



23, 50-52) and its appendages (ib. 53-5s) agree so closely with those which 

 they have always borne as to require no explanation here. The chief 

 surprise of the anthropotomist will be occasioned by their being included 

 amongst the bones of the head. That the upper or pectoral extremity 

 and its supporting arch form actually integrant parts of the occipital seg- 

 ment of the skull, will be proved in the memoir on the general homologies 

 of the bones of the head. I may, here, however, in reference to the terms 

 ' ulna' and ' radius,' request the anatomist to compare the skeletons of the 

 perch or cod with that of the porpoise. The pectoral extremity is in the 

 form of a fin, and in both fish and marine mammal it is applied, in a state of 

 rest, prone to the side of the trunk ; in this position it will be seen in the 

 Delphinus, that the radius is downward, and the ulna with its projecting 

 olecranon upwards. I take this as the guide to the homology of the two bones 

 that support the carpal series of the pectoral fin in fishes. Cuvier, however, 

 gives the name of ' cubital,' perhaps on account of its angular olecranoid 

 prolongation, to the lower bone, and 'radial' to the upper bone: and in 

 these determinations he is followed by M. Agassiz. Roth bones coalesce 

 with the supporting arch in the lophius and some other fishes ; and since, in 

 the lophius, two of the carpal bones are unusually elongated, Geoffroy mistook 

 these for homologues of the radius and ulna. The condition of the pelvic 

 member or ventral fin is, in fact, here repeated in the pectoral ; there being 

 no homologous segment of thigh or leg interposed in any ventrals between 

 the supporting (pelvic) arch and the fin-rays representing the tarso-me- 

 tatarse and phalanges. The earlier stages in the development of all loco- 

 motive extremities are permanently retained or represented in the paired fins 

 of fishes. First the essential part of the member, the hand or foot, appears : 

 then the fore-arm or leg ; both much shortened, flattened and expanded, as 

 in all fins and all embryonic rudiments of limbs : finally comes the humeral 

 and femoral segments ; but this stage I have not found attained in any fish. 

 It is with considerable doubt that I place, qualified by a note of interroga- 

 tion, Cuvier's " troisieme os qui porte la nagoire pectorale" as the homologue 

 or rudimental representative of a ' humerus.' Normally, I believe this proxi- 

 mal member of the radiated appendage of the scapular arch not to be di- 

 stinctly eliminated from that arch in the class of fishes. The Siiuroids are 

 examples of a similar confluence of the first segment (preoperculum) of the 

 diverging appendage of the tympanic arch with that arch. With regard to 

 the lower, distal or apical element of the scapulo-coracoid arch, always the 

 largest bone of the arch in fishes, Cuvier's idea that it is the ' humerus,' far 

 less accords with the law of the development, the connections, and the essen- 

 tial nature of that bone, than the more prevalent view, that it represents the 

 clavicle: a view entertained by Spix, Meckel, and Agassiz, by Wagner, 

 who calls it ' vordere Schliisselbein,' and by Geoffroy, who calls it ' furculaire.' 

 I have, however, been induced to regard the lower element of the scapular 

 arch, in fishes (fig. 5, 52), as homologous with that bone, the ' coracoid,' which 

 progressively acquires a more constant and large* development in descending 

 from mammals to fishes, and which is manifestly a more essential part of the 

 arch than the clavicle, since it is more constant in its existence, and always 

 more completely developed in birds and reptiles ; and especially since it con- 

 tributes more or less of the surface of attachment for the radiated appendage, 

 which the clavicle never does. With reference, also, to the Cuvierian deter- 

 mination of the haemapophysial portion of the occipital inverted arch in fishes, 

 this is unquestionably as essential an element of the arch as is the ' coraco'ide ' 

 in other vertebrates ; and it is the most important part in the piscine class, in 

 no member of which does it present the slightest approach to the character of 



