1014 MESSES. B. C. A. WINDLE AND F. G. PABSONS OS [DeC. 19, 



22. The pectineus is often double. 



23. The adductor cruris is single. 



24. The semitendinosus has only au ischial head. 



25. The femoral head of the flexor cruris lateralis is absent. 



26. The tenuissimus is present. 



27. The extensor longus digitorum has a femoral origin. 



28. The extensor brevis digitorum is always tarsal in origin. 



29. The peroneus longus has no definite femoral origiu, its tendon 

 passes across the sole. 



30. The gastrocnemius has fabellae. 



31. The plantai'is is present. 



32. The flexor brevis digitorum is continuous with the plantaris 

 in the sole. 



33. The tibialis posticus is double. 



34. The accessorius pedis is fibrous. 



With the object of rendering comparison more easy we have 

 arranged some of the more important muscles in a tabular form 

 (p. 1015). 



"We have now to consider what lessons may be learnt concerning 

 the relations and systematic position of the animals included in 

 the order of the Edentata from the study of the muscles. 



JFlower (Proc. Zool. Soc. 1882, p. 358), in a paper on the mutual 

 affinities of the animals composing this order, says that " the two 

 Old-World forms Manidce and OrycteropodidcB are so essentially 

 distinct from all the American families, that it may even be con- 

 sidered doubtful whether they are derived from the same primary 

 branch of mammals, or whether they may not be offsets from some 

 other branch, the remaining members of which have been lost to 

 knowledge." In using the muscles in the endeavour to deal with 

 this problem, the first consideration necessary is to ascertain 

 whether there are any departures from the generalized arrangement 

 of mammalian muscles which are common to all the families of this 

 so-called order, for, if such exist, they are not likely to be adapta- 

 tions to similar conditions of life in animals far removed in 

 relationship. For instance, if similar wanderings from the gene- 

 ralized mammalian arrangement of muscles can be found in the 

 Pangolin and the Sloth, these wanderings are more likely to be the 

 result of kinship than of an adaptive modification to meet similar 

 conditions of life, for few animals more dissimilar in their habits 

 could be imagined than these two. Everyone who has worked at 

 Edentate myology will at once think of two curious muscular 

 modifications which are not usually found elsewhere amongst the 

 Mammalia, namely, the rectus thoracis lateralis and the femoral 

 head of the flexor cruris lateralis, or biceps. Both these muscles are 

 present in the two families, although, so far as we know, the rectus 

 thoracis lateralis is never found as a distinct muscle outside the 

 order with which we are now concerned, whilst the short head of 

 the flexor cruris lateralis is only to be seen in the Edentates, 

 Platyrrhine Monkeys, and Anthropoids. There are other peculiarities 



