MAY, 1921. AMERICAN MARSUPIAL, C^NOLESTES OSGOOD. 89 



pubic symphysis. This scarcely equals the diameter of the acetabulum. 

 The general proportions of the pubes and ischia are thus essentially 

 similar to those in various edentates and insectivores. The rami of the 

 pubis and ischium together with the body of the ischium form a nearly 

 equilateral triangle having its angles respectively at the ischial tuberos- 

 ity, the pubic symphysis, and the cephalic border of the acetabulum. 

 The pubic ramus is very slender and is slightly ridged on its lateral 

 surface. The ischial ramus is slightly wider and more compressed and 

 the body of the ischium is a trifle more so, but all these bones are 

 relatively slender and the obturator foramen which they enclose is large 

 and subtriangular. The ischial rami are not greatly divergent but more 

 nearly approach the perpendicular than those of any other marsupial 

 and in this respect show resemblance to certain insectivores. The 

 ischial tuberosity is fairly well developed and in some specimens forms 

 a decided protuberance. 



The ilium is slender and of the ordinary prismatic shape, being 

 somewhat flattened and everted at the tip. Its ischial border forms a 

 high ridge continuous with the inner edge of the ischium and to some 

 extent overhanging the anterior part of the obturator foramen in shelf- 

 like manner. A slight lliopectineal tubercle is present. The acetabular 

 border of the ilium forms a fairly well marked ridge, especially ante- 

 riorly where it separates the gluteal and iliac surfaces of the ilium. The 

 acetabulum and cotyloid notch are of the usual character. 



The marsupial bones are well developed, their unusually long straight 

 bases being attached to almost the entire anterior edge of the long 

 ascending pubic ramus, that is, from the symphysis to a point directly 

 below the acetabulum and caudad of the iliopectineal tubercle. The 

 base of the marsupial bone is thus almost as long as the anterior pro- 

 jecting spine and proportionally longer than in any other marsupial. In 

 a male specimen, the marsupial bone measures 5.6 mm. in length as 

 against a base of 4.8 mm., the ratio of base to length being 85.7. This 

 ratio is approached only in a few forms in which the marsupial bones are 

 notably rudimentary. The following ratios indicate how widely C&no- 

 lestes differs from the majority of marsupials in this respect : C&nolestes 

 85.7; Didelphis, 40; Dasyurus, 34; Myrmecobius, 15; Sminthopsis, 52; 

 Perameles, 14.2; Trichosurus, 41; Phascolarctos, 37.3; Petrogale, 9. 



ARM AND FOREARM. 

 Plate XV. 



In proportion to the' size of the animal, the humerus is large and 

 heavy, being much the largest single bone in the body. It differs con- 

 spicuously from that of most marsupials in its great degree of curvature 



