132 The American Naturalist. [February, 



On my recent visit to London 3 I took the opportunity to examine 

 both of the types of HyrSbotherium (H. leporinum and H. (=Pliolo- 

 ph tu mlpieeps). In general the external cusps of the superior molars 

 in both forma is lenticular in section, being considerably drawn out 

 anteroposteriorly, and the intermediate tubercles are well extended 

 transversely. In the drawing of the type specimen of H (=P.) vulpi- 

 ceps the molars are represented as greatly enlarged, and their internal 

 portions shown as complete. In the original specimen the teeth are 

 damaged internally, and it is with some diffiulty that the form of the 

 cusps can be made out. However, I am satisfied that the internal cusps 

 are not really huiioiluut u- shown in the plate, but like the American 

 forms of tltjrurnthi ri>nn these cusps are extended transversely and form 

 by wear slight i mediate tubercles. In comparing 



the upper molars of both types of Hyraeotherium of England with those 

 of the Wasatch of America, I find them to be in exactly the same stage 

 of evolution as to the form of the cusps. 



Lydekker 4 speaks of the posterior transveise crest <>f the upper molars 

 in the type of H. (=P.) vuljmepsaa not being represented as sufficcntly 

 well developed in the plate, but this crest on the last molar is drawn 

 correctly, and on the other two molars it is as nearly as well developed. 

 A comparison of the upper molars in both types of ILmtoMherium with 

 those of Euprotogonia, reveals the fact that the form of the cusps in the 

 former genus has undergone a progressive change ; and this is seen 

 especially on the last upper molar which is quadritubercular with a 

 large development of the metaloph, whereas in Euprotogonia the last 

 upper molar is tri tubercular. Again the third upper premolar in the 

 Knu'li.-h tv[ H .-> <if IIi/r<i':ot/n rhini is tritubercular whereas in Euproto- 

 gonia, this tooth has only one external cusp. 



The species of H. (= Plinlophu*) mfpictps is of importance, as 

 in this specimen we have both upper and lower teeth belonging to the 

 same individual. I should like to particularly emphasize the point 

 that the last lower premolar in the type of Pfiotophua is Ampler in 

 .-■trurturr tluiii fheprd true mo/nr, the posterointernal ru.<p beinq <ih*t>nt. 

 This character distinguishes this type from some forms of the American 

 Wasatch which have been referred to Pachynolophus. 



3 1 wish to ex|>r»-H- h, MV my thank- for the privileges I enjoyed in examining 

 specimens in I ty to thank Sir 



W. H. Flower for his kindness. I am also indebted to him for having been able 

 to visit the Royal College of Surgeons. Mr. C- W. Andrews of the I r«ologic*l 



