HArLODONTlDiE— TAXONOMIC CONSIDERATIONS. 551 



"strangely relegated it" to the Hystricine series of Rodents. Dr. T. Gill 

 (7. 5. c.) followed Lilljeborg in 1872 in recognizing a family Haploodontida>, 

 the taxonomic value of which he raised still higher by separating it from 

 other Glires as the type and sole member of a " superfamily " Haploodontoidea, 

 coming next after Castoridce, also made the basis of a superfamily Castoroidca. 

 Lastly, in 1876, Mr. Alston (/. s. c.) endorsed a family Haplodontidte, which 

 he placed next to Castoridce among Sciuromorpha. 



To waive for the moment the question of absolute rank of the type 

 Haplodon, nothing in the way of classifying the Rodents seems to me clearer 

 than that the affinities of Haplodon are with Castor, and that both these 

 genera appertain to the Sciurine "series", "superfamily", or "line of develop- 

 ment" — at any rate, neither to the Murine nor to the Hystricine series; the 

 next nearest relationship of Haplodon being with Arctomys, and so with the 

 Schiridce itself. The more or less complete agreement of such views with those 

 of the writers mentioned in the foregoing paragraph will be evident without 

 further comment ; the better informed authors have, in fact, differed less among 

 themselves respecting the immediate relationships of Haplodon and Castor than 

 in regard to the location of these forms in the general series of simplicidentate 

 Rodents ; Haplodon, at any rate, whether considered as genus or as family, 

 having been relegated successively to (1) the Sciurine, (2) the Murine. (3) 

 the Hystricine series, and (4) having formed the type of a different series 

 from any of these; this, too, at the hands of those who are at one respecting 

 its immediate affinities. 



This brings up the question of the absolute standing of Haplodon. Is 

 it referable to one of the established series of Rodents, or is it to stand alone 

 as the representative of a separate series'? Regard for a very strict equiva- 

 lency of groups might urge the latter appreciation of the value of the pecul- 

 iarities of Haplodon; and, in the sense that the family Haplodontidce differs 

 more from all other families of Rodents than those of the same series usually 

 do from each other, Dr. Gill's special superfamily Haploodontoidea may be jus- 

 tified. But, practically, no exact equivalency of groups is attainable; and, if 

 it were, I should not be satisfied of the necessity of considering Haplodon to 

 represent a separate series from the Sciuromorpha, in view of the closeness of 

 relationship which I insist is found between Haplodont'uhe, Castoridce, and 

 Sciuricke. 



In so stating, it becomes necessary to give my appreciation of the limits 



