ANATOMY OF CACOPUS SYSTOMA. 



537 



muscles, viz., the obliqtms-intermcs, the inner portion of the 

 sternohi/oideus,^^ sternocor7iuoideus ," and the " abdominis-sternalis," 

 the last three to be described later in the section on muscles. 

 This probably accounts for the unusually large size of this xiphi- 

 sternal plate (text-fig. 7 A). 



The " crista medialis," a ridge of the humerus which, accord- 

 ing to Ecker (4, p. 42), occurs among the males of three Euro- 

 pean sjDecies of Rana as a sexual difference, is not to be found 

 in the males either of R. hexadactyla or of G. systoma. The 

 wrist-bones of the latter show greater calcification than those of 



Text-figure 7 (A and B). 



A. 



A. The pectoral girdle of Cacopus systoma. X., xiphisternum ; C, coracoid ; 



S., scapula ; S.S., suprascapula ; B., an apparently bonj'' portion of the latter. 



B. The bones of a manus of Cacopus systoma. S., a sesamoid bone situated in a 



tendon ; H., vestigial first finger. For other letters consult the key-list of 

 abbreviations. 



Rana ; they also exhibit certain differences in their shape and 

 in the details of their articulation with one another. In addition 

 to the three bones of the proximal row mentioned by Ecker, one 

 very often finds a fourth bone, which is exceedingly small, 

 situated above and between the os pyramidale and the os lunatum. 

 This may be a sesamoid bone, as it is placed in the course of a 

 tendon (text-fig. 7 B). 



In the pelvic girdle the absence of the iliac crest is remarkable 

 when one finds that none of those muscles connected with the 

 same crest in Rana is absent. "Whether this crestless condition 



