170 



MR. F. a. PAESONS ON 'i'HE 



[Jan. 14, 



these eombiaed muscles ia the various aaimals dissected are the 

 following : — 



Mijoxus 2-7 ( 



C'ricetus 3-7 



Oerbillus 2-7 



Microtus 2-7 



Myodes 2-7 



Mils larbarus 2-7 



„ rattus 2-7 



Ehizomys 1-7 



Oeorychus 3-7 



Bathyergus 3-7 



Heteromys 2-7 



1-7 ribs. 



1-7 



1-8 



1-8 



1-8 



1-7 



1-7 



1-8 



1-10 



1-10 



1-8 



Sei-ratus Posticus. — In the Myomorpha the anterior part of this 

 muscle is always present and well marked ; it is usually inserted 

 into the ribs from the 4th to the 7th, but iu Crketomys it is 

 continued back to the 9th, and in Bhizomys to the 11th. In 

 Oeorychus and Bathyercjus it is inserted into the 6th, 7th, and 8th 

 ribs. The posterior part of the serratus posticus was only seen in 

 Microtus, Bathyenjus, and Myodes ; in the first it was inserted into 

 the last 4, and in the two latter into the last 5 ribs. 



Fig. 10. 



Lev.ano.scap. 



Sefv post. 

 Nock-muscles of Ilftnistei'. 



