1896.] Geology and Paleontology. 309 



prove that Mlrtotherium is a valid genus and entirely distinct from 

 either Diplobune or Dacrytherium. 



The genus Adiotherium was described by Filhol in 1884. This 

 genus is referred by Zittel to the milk dentition of Dacrytherium, I can 

 not agree with Prof. Zittel on this reference either, as I believe Adith 

 therium to have been based upon the milk dentition of MLcMJu-rium. 



The skull in Mixtotherium is essentially Suilline, but exhibiting some 

 characters like those of the Anoplotheroids. The form of the brain 

 case is longer and narrower than in Cebochoerus, and it closely resem- 

 bles that of Acotherulum which is one of the most primitive of the early 

 Suillines of Europe. The occipital region of the skull in Miztotkt > turn 

 is much broader than high, and is not constricted in the middle as in 

 [ktcryth* riant ; the occiput has nearly the exact form of Acoth, rulam 

 and Cebochoerus. 



In the primitive pigs of the Phosphorites the auditory bulla? are 

 extremely small, in Mixtnfherium they are large. The basioceij'ital 

 region of the skull in Mixtotherium is rather long and narrow, and like 

 that of Dacrytherium. In Cebochoerus of the Phosphorites, the pecul- 

 iarly elongated and constricted snout of the pigs is well differentiated, 

 however, in Mixtotherium as well as Acotherulum the facial region of 

 the skull is broader and shorter, its form being more as in Daerytherivm, 

 Mixtotherium agrees with Diplobune and differs from Dacrytherium in 

 lacking a preorbital fossa in the maxillary bone. The general form 

 and proportions of the skull in Mixtotherium is very much like that of 

 the peculiar American genus, Oreodon. 



The dentitin ,:'.!/ *<> • resembles that of the . !/«./// .*'<• "'« 



in the absence of any diastemas, it differs, however, from this family in 

 the large size of the canines, which in form resembles more those of the 

 Suillines. The superior premolars are normal in form, and not elon- 

 gated as in the Anoplotheroids. The last upper premolar closely 

 resembles in structure a true molar, it has two external cusps, which 

 are intermediate in structure between the bunoid and selenoid forms. 

 The deuteroconid forms a crest with the antero-intermediate tuber- 

 cle, the tetastoconid is present, but small and bunoid in structure. 

 The structure of the superior molars ler from those 



of Dij.hfnnn and Dacrytherium in the following details ; the external 

 crescents are united externally by a prominent mesostyle, which is more 

 constricted than in Diplobune; in Dacrytherium this portion of the 

 molar is open widely internally. 



In the AnoplotheridoB the protocone is distinct from the protoconule, 

 whereas in Mixtotherium these elements are united and form a well 



