1871.1 317 [Wilder. 



The foregoing tables are suggestive of some other considerations 

 bearing more or less directly upon intermembral homologies. 



1. From the nature of the parts, especially in Cetacea, and also 

 from the admissions of some observers, it is not always easy to ascer- 

 tain the number of digital phalanges ; it appears also, that the possi- 

 ble morphical value of such information has not always been recog- 

 nized by observers, by reason of the slight telical importance of the 

 individual phalanges; but on the other hand, some have been so ac- 

 curate as to note a difference in the numerical composition of the 

 same digit upon the two sides of the body : (as with the Globioceph- 

 alus described by Keinhardt). 



2. The distinctions between metacarpals and phalanges, in respect 

 to length and mobility, which exist with the higher Mammalia, do not 

 appear with the Cetacea; with Glob, swineval, according to Macallis- 

 ter, (P. Z. S., 1867, p. 481), the exact " number of phalanges could 

 not be reckoned," and the only synovial capsule was at the omos; 

 and in describing the armus of Balcena mysticetus, Eschricht and 

 Reinhardt state that the minimus "is in direct contact with the 

 ulna," . . . and they are led to suppose that " not only the car- 

 pus and digits, but also the bones of the forearm have all been 

 formed in the beginning from one continuous cartilage, and that, at 

 all events, we cannot here expect fixed or quite immutable relations 

 between individual bones." (Ray Soc. Mem., p. 131.J 



3. While there seems to be no objection to admitting the special 

 homology of the cetacean digits with those of other Mammalia, there 

 appears to be no way of determining the special homology of individ- 

 ual phalanges even within the Cetacea themselves; for, allowing a 

 margin for inaccuracies of observation and statement, there is never- 

 theless a considerable discrepancy in this respect between members 

 not only of the same order and family, but also of the same genus 

 (Delphinus, for instance) and species (Phy solus antiquorum). 



4. The taxonomic value of the numerical composition of the 

 digits must be regarded as very low with the Cetacea; it may be said 

 that this conclusion would not necessarily apply to the other Mamma- 

 lia, but it would not be easy to prove this, since they are members of 

 one and the same class ; the Cetacea do not present exactly the case 

 of the Cheiroptera, because the usual number, three, is never ex- 

 ceeded in this group, and although it is not now certain which of 

 the phalanges is missing, yet there appears to be no reason why this 

 matter may not some time be decided; but I see no way of ascertain- 



