378 Wortman — Studies of Eocene Mammalia in the 



rather than the carnassident formula.* The dorsals are twelve 

 in number, and of these the neural spine of the first is broad, 

 flat, and greatly elongated ; it is the longest of the series, those 

 of the succeeding vertebrae gradually decreasing in height to 

 the eleventh or anticlinal vertebra. The spines have a very 

 backward slope up to this point, where they change abruptly 

 to a forward direction. This, as far as I am aware, is the 

 point at which the anticlinal occurs in most of the Carnassi- 

 dents. On the eighth dorsal, metapophysesmake their appear- 

 ance and increase in size posteriorly, but there are apparently 

 no representatives of the anapophyses developed. 



The lumbars are seven in number ; they have short, broad, 

 neural spines and heavy, keeled centra, increasing in size from 

 before backward to the antepenultimate, which is the largest. 

 The transverse processes are long and thin, with a forward and 

 downward direction. The zygapophyses are powerful and, as 

 Cope has observed, are closely interlocking. The articulation 

 is effected by means of the half-cylindrical postzygapophyses 

 fitting into half-cylindrical prezygapophyses. They differ 

 materially from those of some other Creodonts, notably 

 Patriofelis, in which they are sigmoid in cross-section. 



The sacrum is somewhat damaged, but enough remains to 

 show that the auricular process was large and rugose, that the 

 spines were of moderate size, and that there were very prob- 

 ably three vertebrae entering into its composition. It is rela- 

 tively very narrow. The caudals are much weathered and 

 many are missing. The proximal ones are short and propor- 

 tionally but little larger than those of the dog. Those from a 

 more posterior position are long and slender, but not much 

 more so than those of many of the modern Carnassidents. 

 There is no means of judging of the length of the tail, but in 

 comparison with such a type as Patriofelis, the tail was 

 reduced and slender. This supposition comports well with 

 the highly-developed cursorial habits of these forms. 



Ribs and Sternum. — There are twelve pairs of ribs, and for 

 a member of the Carnivora, the anterior ones are remarkably 

 broad and flat; they are, indeed, much more like those of an 

 Ungulate than a Carnivore. The first is short and stout. The 

 third is the broadest, those posterior to it becoming gradually 

 narrower to the eighth, which is slender and subround in trans- 

 verse section. All the ribs have a well-developed tuberculum 

 and capitulum, with the exception of the last three, in which 

 the tuberculum is absent. As compared with that of the dog, 

 the capacity of the thoracic cavity was apparently considerably 

 smaller. Some four or five of the sternebrse, figure 45, are 



* An exception to this must be made in the case of Oxycena lupina, in which 

 the formula is the same as in the Carnassidentia. It is probably likewise true 

 that its successor Patriofelis had the same formula. 



