250 H. G. SEELEY ON THE DINOSAURS 



the shaft is concave from side to side posteriorly ; the concavity, 

 diminishing in amount, extends proximally towards the region of 

 the lateral trochanter. The width of the shaft just above the con- 

 dyles is under 9 cm. (3^ in.) ; and the median thickness of the shaft 

 is under 5 cm. (2 in.). The two sides of the shaft converge a little 

 towards the base of the lateral trochanter ; and the sides converge 

 upward towards the anterior surface so as to give the front of the 

 bone a convex or subcylindrical aspect in its middle third. Dis- 

 tally, towards the condyles the front of the bone is gently concave ; 

 but the concavity narrows and deepens rapidly to descend between 

 the anterior expansions of the condyles, which are broken away. 



The lateral trochanter and muscular ridge (fig. 2, a, b, 1 1) ex- 

 tends to within 19 cm. (7fin.) of the distal end, is nearly 14 cm. 

 (5^ in.) long, and extends to within about 15 cm. (6 in.) of the 

 proximal end. It is a compressed curved process which is directed 

 mainly backward and a little inward, and is much more developed in 

 its distal half than in the proximal part. It owes its existence to 

 two powerful muscular attachments, which are on the inner side of 

 the bone ; they partly overlap each other, so that the proximal scar 

 descends partly in front of the distal impression. The proximal scar 

 is about 8 cm. (3j- in.) long, and 3 cm. (l^-in.) wide; less than half 

 of its width is attached to the trochanteric process. The distal scar 

 is quite as long and as wide, but is pointed proximally, rounded dis- 

 tally, is much deeper, and is chiefly attached to the trochanter (fig. 2, 

 b, I t). The posterior edge of the trochanter, which is inclined ob- 

 liquely backward (fig. 2, a), is nearly parallel to the anterior borders 

 of the muscular scars. The width of the shaft just below the tro- 

 chanter is 6 cm. (2 T 4 T in.) ; its thickness in the same position is 

 5 cm. (2 in.). 



Proximally, above the trochanter the form of the shaft alters, 

 becoming compressed and well rounded on the inner surface, and 

 greatly widened on the external border, so that the transverse 

 section is subtriangular (fig. 2, c) ; the anterior surface is broadly 

 concave, with the concavity increasing as the proximal trochanteric 

 ridge is developed externally ; the posterior surface is flattened, with 

 a moderate median longitudinal concavity ; and the external surface 

 is flattened along its whole extent, but is a little convex from above 

 downward, and has a broad shallow concavity behind the lateral tro- 

 chanter. 



"No. 42957. A second specimen is smaller, and worth describing 

 because it shows the form of the distal end (fig. 2, d). 



This fragment consists of the shaft and distal end of a Dinosaurian 

 femur of moderate size. The fragment measures 30 cm. (ll-|in.) in 

 length, and extends for about 3 cm. (14- in.) beyond the internal 

 lateral trochanter. The shaft is more quadrate in section than in 

 the larger specimen, is more concave on the inner margin, has a slight 

 convexity in length on the external border, and exhibits various 

 minor details of structure. 



The width of the shaft just below the lateral trochanter at 13 cm. 

 (5J in.) from the distal end is 3^- cm. (11 in.) ; the thickness in the 

 same position is just over 4 cm. (1^-in.). 



