612 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxxvi. 



Pfnodus, a genus of the Plagiaiilacidse, was proposed by Cope in 

 1881, the t3'pe-species, P. )nedi(eri(s, being founded on a single lower 

 premolar, p^, from the Torrejon beds of New Mexico. Other speci- 

 mens, some representing the complete lower dentition, have since 

 been referred to this species, but the upper dentition has not been 

 known. In 1884 Cope proposed a second genus, Chirox, basing the 

 type-species, C. plicatus, on a series of three upper premolars. This 

 and a second specimen, consisting of a palate containing most of the 

 upper dentition, which was later described and figured by Cope, con- 

 stitute the principal material referred to this second genus. Both 

 specimens are from the same beds as those from which the type of 

 Pfilodus mcdifpims was obtained. In 1887 Cope*^ questioned whether 

 the specimens refered to Chirox might not belong to PtUodns., but 

 deciding they did not, proposed a new family, the Chirogida^, for the 

 former genus, which he considered allied to the Polymastodontidse, 

 regarding the family as a connecting type between the Plagiaulacida? 

 and the Polymastodontida^. In classifying the Allotheria in 1888, 

 Osborn^ placed Chirox in the Bolodontidse, a family proposed by him 

 in 1887.^ 



It is thus evident that the uncertainty regarding the relationships 

 and sytematic position of these species has been considerable. The 

 confusion, however, has been largely due to lack of associated mate- 

 rial, therefore it is with more than ordinary interest that we come 

 to examine the present specimen from Montana, in which the com- 

 plete upper and lower dentition has for the first time been found in 

 undoubted association. This specimen has the lower jaws and teeth 

 of Pfilodus and the upper teeth of Chirox, a fact that has not been 

 wholly unsuspected, though none the less interesting and important 

 in the confirmation. Thus, in proving the sj'nonomy of these two 

 genera the family Cliirogidse, proposed by Cope, is finally and satis- 

 fiictorily disposed of. Incidentally, it also apparently confirms indi- 

 rectly the opinion expressed by Marsh '^ regarding the probable iden- 

 tity of the genera Bolodon and Plagiaulax. This opinion, which he 

 gave in criticising Osborn's classification of the Mesozoic ^Mammalia, 

 is expressed as follows: '"A careful study, moreover, of the knoAvn 

 species of the true Plagiaulacidw Avould have shown him the strong 

 probability, at least, that the genus Bolodon, which he makes the 

 type of a distinct family, is based on the upper jaws of PlafiiaulaxP 

 This supposition now seems confirmed, for, as is generally con- 

 ceded, PtiJodiis bears an undoubtedly close relationship to the much 

 older form Plar/iaulax, known only from the lower teeth, while 



« Anier. X.nturalist, XXI, 18S7, p. 5G7. 



&Journ. Acad. Nat. Sci. Phila. (2), IX. Tt. 2. 18SS, p. 219. 



^ Proc. Acad. Nat. Sci. Pliila., 1SS7, p. 2S5. 



^ Idem, 1891, p. 239. 



