160 MB, F. G. PARSONS ON THE - [Jail. 14, 



The following is a list of the animals dissected for the first part 

 of the present paper : — 



Myoxm dryas. 

 OerbUliis shawi. 

 Cricetus friimentarius. 

 Cricetomys gambianns. 

 Microlns amphihius. 

 Myodes lemmus. 

 Mus decumanus. 



Mus rattus. 

 Mus barbarus. 

 Rliyzomys badius. 

 Qeoryclius capensis. 

 Batliyergus maritinius. 

 Heteromys longicaudatus. 



Also 



Lepus timidus and Lepus cuniculus 



for the sake of comparison. 



Accounts of the muscles of other animals hy various authors 

 have been used and their sources acknowledged in the text. 



Muscles of the Head and Neck. 



Temporal. — In all the Myomorpha the three parts of the tem- 

 poral are more closely fused than they are in the Sciuromorpha, in 

 this respect resembling the Hystricomorphine arrangement. 



In the Water- Vole the parietal part of the muscle is very large 

 and arises from the temporal fascia, as well as the parietal, maxil- 

 lary, and frontal bones. It runs down as a flat tendon to be 

 inserted, opposite the anterior molar teeth, into the mandible. 

 The anterior deep part of the masseter, after coming through the 

 infraorbital foramen, joins this tendon. 



Kg. 1. 

 PaHiet*\. part of Temp. 7^'^'"' 

 ANT.de EP MAS. 



■---^OST.SUP.MAS. 



>NTsup. mXs. i '^'^^H 



POST DEEP MA.a, 



Masticatory muscles of Vole. 



In the MyoxidsB and Muridse the muscles of opposite sides are 

 separated by an interval which is often, as in Mus rattus, of 

 considerable extent. In the Spalacidae, on the other hand, the two 

 muscles rise close together, and the superficial layer described by 

 Allen ' is distinct and rises by aponeurosis from the sagittal crest. 

 These animals, moreover, bear out the statement in Broun's 



' Pr. Acad. Nat. So. of Philadelphio, vol. iii. p. 386. 



