and its Natural Affinities. 373 
a succession which I believe to be sufficiently natural, although, 
strictly speaking, every arrangement in a single series is de- 
fective. 
Finally, since the anatomical materials respecting the genera 
of North America are very much dispersed (being contained 
partly in journals and memoirs of societies and academies not 
always to be found in the very largest of public libraries), it 
would be very desirable to have collected together all that has 
been published upon these doubtful reptiles of America. There 
would then remain another undertaking, viz. to arrange in a 
systematic form all that we now know concerning the various 
forms of this small group*; and this, though a work of com- 
pilation, could be executed only by an able naturalist. 
The labours of Rusconi with reference to the Proteus are well 
known ; but, as regards the other genera, the Cryptobranchus of 
Japan is almost the only one of which we have any complete 
anatomical details, viz. those which we obtain through the re- 
searches of the three physicians of Rotterdam, published by the 
Société Hollandaise, and from the admirable work of one of the 
greatest anatomists of our time, Professor Hyrtl of Vienna. 
It is to be lamented that there still reigns some confusion 
throughout much of what has been published respecting these 
doubtful reptiles, and even in works of well-merited celebrity. 
It is stated in the ‘Erpétologie générale’ that I have figured 
the nuchal fissure in the Cryptobranchus of Japant+, whereas the 
entire plate, and consequently also the figure cited, refers to the 
North-American species. The work of Duméril and Bibron 
having certainly a much more extended publicity than my 
Dutch memoir, I have thought it advisable not to neglect the 
present occasion to remove this error, and the more so since I 
by the great number of their vertebrae. Cuvier counted 86 vertebra in 
the Siren, 99 in Amphiuma tridactyla, and 112 in Amphiuma didactyla 
(Mém. du Muséum, xiv. p. 8). 
* Unless we suppose that the genus Proteus contains several species 
(Fitzinger, “‘ Ueber den Proteus anguineus der Autoren,” Sitzungsberichte 
der mathem.-naturw. Klasse der Kaiserl. Akad. der Wissenchaften, October 
1850), the entire group numbers scarcely ten species. I know not what 
to think of the eight species of Necturus which Rafinesque affirms to 
exist in the United States (Journal de Physique, Ixxxviii. p. 418); but 
they have not been noticed by those who have written about the fauna of 
North America since his time. 
t “Il n’y aurait done de différence que dans l’absence du trou collaire 
que M. van der Hoeven a figuré pl. 2. fig. 8,” &c. (ix. p. 164). 
{ I regret extremely that Prof. Duméril, the venerable veteran who 
honoured me with his friendship, did not consult my “ Fragments zoo- 
logiques,” in the third volume of the ‘ Mémoires de la Socicté de Stras- 
bourg’ (1840), where my memoir on the Pseudosalamander, the great 
Japan reptile, is translated entire. 
