OF THE MESOZOIC MAMMAI4A. 
237 
generof. Coronoid slender. Condyle elevated. Angle small and separate, extending 
posteriorly vntliout infieetion. 
This family embraces the closely allied genera Stylacodon, Phascolestes, Dryolestes, 
Aesthenodon and Laodon. While possibly embracing also the Amblotheriidoe, it is readily 
distinguished from the Triconodontidce, Peralestidce and Amphitheriidoe by the pat- 
tern of the molars, which consists of two or three internal cusps, the anterior pair 
of which are connected by transverse ridges with a single styloid external cusp, 
the upper molars reversing this arrangement. The definition is as above. 
STYLACODON, Owen.i 1866. 
Dentition. — i c pm j, m The incisors have very much elongated spatu- 
late crowns and are compactly placed. The canine is long and semi-procumbent. 
The premolars have pointed, recurved crowns, 
and are slightly separate. The inner face of 
the molars shows three internal cusps (Marsh). 
The species S. gracilis (Marsh) has a distinct 
„ T ft 1 " 1 j eighth molar, which is represented by a fang 
Figure 26. Left lower jaw of Stylacodon gra- _ ° ^ ° 
cUis, Marsh; outer view, three times natural some of the English specicS,^ showing that 
this tooth is probably late in coming into place. 
'I'he jaw is very slender with a nearly straight, lower border, and very elevated condyle. 
PHASCOLESTES, Owen,' 1871. 
Syn. (probable), Dryolestes, Marsh, 1878. 
Dentition — i c j, pm m The incisors are separate with the crown ex- 
panding at the tip. The median is the largest, the second is the smallest, the third 
and fourth increasing in size. The canine is lofty and recurved. Behind this is a 
deep depression of the alveolar border, 
with two rudimentary premolars. The 
third and fourth premolars are very 
large. The first molar is very small. 
The matrix shows the impression of 
the external styloid cusps of to m^. 
The jaw is massive with a rounded 
lower border. The Dryolestes vorax. 
Figure 27. Leftlower jaw of Marsh; outer Marsh (Am. Jur. Mamm., Plate IX, 
and inner views, three times natural size. fig. 4), is very similar to PJiascolestes, 
and it is probable that these genera will prove to be the same upon further evidence. 
^Stylodon, Geological Magazine, or Monthly Journal of Geology, May, 1866, p. 199. Syn. Stylacodon, 
Marsh. “ Am. Jour. Sc.,” 1879, p. 60. 
See “ Mesozoic Mammalia,” p. 61. Also Plate II, fig. 18 a. 
> Doubtfully separated from Peralestes, by Professor Owen, p. 35. 
