i895. MUSCLES AND CLASSIFICATION. 341 



study of their muscles negatives the idea entirely. In addition to the 

 scapulo-clavicularis and the digastric and transverse mandibular 

 points of divergence, the Chinchillidae have two heads to the biceps 

 cubiti, the jerboas only one; in the Chinchilhdse the biceps is inserted 

 into both bones of the forearm, in the Dipodidae only into the ulna ; 

 in the Chinchillidae the omo-hyoid is absent, in the jerboas it is 

 present ; in the Chinchillidae the tibialis anticus rises from the tendon 

 of the extensor longus digitorum as well as from the tibia, in the 

 Dipodidas it rises only from the tibia. I am pleased to notice that 

 Winge, in his monograph on " The Rodents of Lagoa Santa " 

 {E.Museo Lundii,m., 1888) separates the Dipodidae from the Hystrico- 

 morpha, but for other reasons than those I have brought forward. 



In concluding this paper I must admit that I have founded my 

 generalisations on the study of one Order of mammals ; but this is 

 partly because I have paid more attention to rodents than to other 

 animals, and partly because a general review of myological literature 

 Avould far exceed the Hmits of a paper such as this. My observations 

 on other animals, as well as a study of the literature of the subject, 

 make me think that what is true for one of the largest Orders holds 

 good for the rest. Attention may be directed to a most complete 

 paper by Wilson on the myology of Notoryctes typhlops as compared 

 with that of other mammals, in which the following passage occurs ^ : 

 " I cannot avoid the conclusion that the structural resemblances in 

 particular to certain members of the order Edentata are not all to be 

 explained as merely the coincidences of somewhat similar functional 

 modifications, but are the enduring evidences of a real if distant 

 morphological kinship." This is practically my own view, and I 

 would urge that certain muscles provide a very good clue to the 

 relationships of animals, the great point being to select the muscles 

 on which reliance is to be placed. 



F. G. Parsons. 



St. Thomas's Hospital. 



^ Trans. Roy. Soc. S. Austral., 1894. 



