PTEEODOJSr AFEICANUS. — APTEEODON. 225 



quite as high as the top of the head. The lesser trochanter (l.t.) is a large prominence 

 united with the great trochanter by a strong ridge, which forms the outer border of the 

 deep digital fossa. The shaft is strongly compressed from before backwards, and broad 

 from side to side ; on its outer side, about a third of its length from the proximal end, 

 there is a rugose ridge representing a third trochanter {t.t.). The whole shaft is curved, 

 the convexity being forwards. The distal articulation is very large. The rotular trochlea 

 is narrow and extends far up the front of the bone, as in the femur of Hyanodon 

 figured by Scott (Journ. Acad. Nat. Sci. Philad. vol. ix. p. 523). The tuberosities are 

 large and project strongly backwards, the inner (i.t.) rather the furthest ; they are 

 separated by a broad and deep intercondylar groove. In its general form, particularly 

 in the broad flattened shaft, the bone suggests that the animal may have been to some 

 extent aquatic. It is possible that this femur may have belonged to Apterodon, or at 

 least to the same animal as the humerus provisionally referred to Apterodon, since that 

 bone also suggests possibly aquatic habits on the part of its possessor. The dimensions 

 (in centimetres) of this specimen are : — 



Extreme length 23'2 



Diameter of head 3'1 



Width of proximal end . . . . 7 



„ mid-shaft 3'2 



,, distal end 6 



M. 8887. Plaster cast of the above specimen. Made in the British Museum. 



Genus APTERODON, Fischer. 

 [Bull. Soc. Geol. France, [3] vol. viii. (1880) p. 288.] 



1887. Dasyurodon, A. Andreae, Bericht Senekenberg. naturforsch. Gesellschaft, Frankfurt-a.-M. 

 p. 125, pi. iv. 



The specimens described below agree closely with the figures of the teeth of 

 Dasyurodon given by Andreae. Unfortunately, Fischer gives no figures of his 

 Apterodon, which, from his description, difl'ers a little from Dasyurodon ; but, since 

 most authors regard the two names as synonymous, Apterodon is here adopted on 

 the ground of priority. 



This genus is distinguished from Pterodon by the much slighter development of the 

 cutting-blade of the lower carnassials, due to the smaller degree of compression of 

 the cusps, and also to the much smaller size of the antero-internal cusp ; the talon also 

 is relatively much larger. In these points Apterodon, in fact, seems to be intermediate 

 between forms like Sinopa and Pterodon, just as the latter is intermediate between 

 Apterodon and Hycenodon, in the latter of which the talon is almost obsolete and the 

 two anterior cusps form a sharp secant blade. 



