ON A NEW FOSSIL MAMMAL. 525 



22. On a Mammalian Mandible {Cimolestes cutler i) from an 

 Ujjper Cretaceous Formation in Alberta, Canada. By 

 Arthuk Sbiith Woodward, LL.D., F.R.S., V.P.Z.S. 



[Received and Read May 23, 1916.] 



(Text-figure 1.) 



Index. 

 Systematic : Page 



Cimolestes cutleri * 528 



Structuee '. 525 



Small mammals with a dentition closely similar to that of 

 the existing opossums have long been knowu by fragments from 

 the Upper Cretaceous freshwater deposits of North Amei'ica. 

 Complete jaws, iiowever, are still needed to correlate the isolated 

 teeth which form the majority of the fossils hitherto discovered. 

 An imperfect right mandibular ramus lately obtained for the 

 British Museum by Mr. William E. Cutler is thus of special 

 interest ; and its value is increased by the ' fact that it was 

 discovered in Alberta, Canada, in a somewhat older deposit than 

 the Laramie Formation of Wyoming, U.S.A., in which the 

 previous specimens were found. 



The new mandibular ramus lacks most of the hinder ascending- 

 portion and the extremity of the mandibular symphysis, but is 

 otherwise well preserved, with two of the molars, one premolar, 

 the broken roots of the other molars and premolars, and the 

 socket for the large canine tooth. It is shown of twice the 

 natural size, from the outer, upper, and inner aspects in the 

 accompanying text-figure (p. 526). The mandibular symphysis is 

 much elongated, the facette (s.) extending as far backwards as 

 the anterior root of the fourth premolar. The large mental 

 foramen {m.) on the outer face of the ramus is also situated 

 beneath and just in front of the anterior root of the same 

 premolar. 



The four molars and three pi-emolars behind the canine are 

 arranged in close series, and the teeth presei'ved are considerably 

 worn, showing that the jaw belongs to a fully adult individual. 

 The smooth enamelled crown of these teeth slightly overhangs 

 the root, but there is no cingulum on the outer or inner face. A 

 cingulum is only observable on the anterior and posteiior faces of 

 the two molars, where it slopes downwards and outwards. The 

 fourth molar {m. 4), which must have been at least as large as the 



* [The complete account of the new species described in this communication 

 appears here, but since the name and a preliminary diagnosis were published in the 

 ' Abstract,' No. 158, 1916, the species is distinguished by the name being under- 

 lined. — Editoe.] 



