MERRIAM: THE FAUNA OF RANCHO LA BREA. 



239 



anter and the spiral line below it are always well developed. The tubercle on 

 the postero-lateral region of the shaft just above the popliteal surface is 

 usually clearly marked, and is sometimes very large. Frequently the external 

 epicondylic line passing through this tubercle is extended as a long, narrow 

 sharp-edged ridge. 



The tibia (figs. 19, 20, and 21) is usually characterized by a very prominent 

 cnemial crest which fades out inferiorly in the lower portion of the upper 

 third of this element. No peculiar characters are noted in the fibula. 



The astragalus has much the same form as in Canis pambasileus, excepting 

 in the vertical diameter of the neck. The distal face for articulation with 

 the navicular is transversely elongated in C. dirus to such an extent that the 

 long diameter is about one-third greater than the short or vertical diameter. 

 In C. pambasileus the neck and head are thicker, and the terminal face for 

 articulation with the navicular is more nearly round. 



In the calcaneum the distal face for articulation with the cuboid tends to 

 be a little narrower transversely and more nearly quadrate in form in C. 

 pambasileus than in C. dirus. The cuboid is a little narrower transversely 

 in proportion to its length, and the distal face for articulation with metatarsals 

 four and five somewhat narrower in C. dirus than in C. pambasileus. 

 Corresponding to the form of the head of the astragalus the navicular is 

 relatively narrow anteroposteriorly or vertically in C. dirus. It is also noted 

 that in this species the small posterior facet which meets the calcaneum is 

 relatively larger than in G. pambasileus. The cuneiform elements are not 

 materially different from those of the modern wolves. 



The metatarsals, like the metacarpals, are relatively somewhat shorter in 

 the average specimen of C. dirus than in C. pambasileus, 

 though large specimens are present which exceed the largest 

 measurements known in the latter form. The metatarsals 

 of C. dirus, even where shorter absolutely than in C. pam- 

 basileus, are distinctly wider anteroposteriorly in the upper 

 half of the shaft. Metatarsal I of (7 dirus does not appear 

 to show any noteworthy difference from that of the modern 

 wolves. It is at least as large relatively as in C. pambasil- 

 eus. Metatarsal II (fig. 23) is slightly narrower trans- 

 versely at the proximal articular end than in G. pambasileus, 

 and the angle on the median side of the shaft is less dis- 

 tinctly marked than in that form. Metatarsal IV, in addi- 

 tion to the greater anteroposterior width of the shaft, shows 

 a sharper anteromedian angle in the middle third of the 

 shaft. Metatarsal V (fig. 22) is very distinctly wider anter- 

 oposteriorly in C. dirus than in C. pambasileus and C. occi- 

 dentalis. It is further characterized by the great promi- 



22 



23 



Figs. 22 and 23. Canis 

 dirus Leidy. Metatar- 

 sals, no. 19475, X %. 

 Fig. 22, right metatar- 

 sal five, medial aspect; 

 fig. 23, right metatar- 

 sal two, lateral aspect. 

 Raneho La Brea Beds. 



