‘2 Bulletin American Museum of Natural History. [Vol. XXXIV, 
revive Stypolophus (type S. pungens) and include in it all the Lower Eocene 
species, limiting Sznopa to the middle Eocene. He gives no hint of reason 
for this procedure, nor am [| able to imagine any justification for it. The 
Lower Eocene species are distinguished from their successors by a number 
of skull and skeleton differences which might conceivably be regarded as 
generic, although I do not regard them as such. But the name Stypolophus 
could not be used for them, as its type species is middle Eocene, and closely 
allied to S. rapax, type of Sinopa. 
Key to Species of Sinopa. 
I. Heels of mi» broad-basined, equalling trigonid in diameter. Paand me of m!~2 
well separated. Premolars robust with rugose enamel, p; one-rooted. 
A. Molar shears of similar type, heel of ms broad, me of m3 well developed. 
a. ‘Trigonids of molars robust, not high. 
if. M3 = 295; no. Giasucma-pehind >... ......e.0... . S. major. 
b. Trigonids of molars of moderate height. 
2. Mi-s = 26mm.; a diastema behind p............. S. grangert. 
3. Mis = 28 mm.; nodiastema behind ps......... S. shoshoniensis. 
4 Mig S25 tome fe a AP ee: en ae S. rapaz. 
Ov: “Mass = 20mm. 7 - tae ee elea ames S. pungens. 
B. Carnassials, more specialized with shear more anteroposterior; ante- 
air rior molars with shears little developed. Heel of m; narrow, meta- 
cone of m° vestigial. 
ee ee ty Re ad cots Re ics S. opisthotoma. 
II. Heels of my_3 narrow-basined; trigonids high, and broader than heels. Pa 
and me of upper molars more connate. Premolars higher with smooth 
enamel, p; two-rooted, compressed. 
1. Mis’ = 29 ham.; diastéma‘ behind=ps oS ae 4° S. hians. 
8. Mi_3 = 25-26 mm.; no diastema behind [epee oe: S. strenua. 
III. Smaller species of intermediate type, but nearer to division ii. 
9. Mi_3 = 21.5 mm.; premolars more robust, symphyseal region 
shorter and deeper, m+ less reduced.......... S. multicuspis. 
10. Mis = 20-22 mm.; premolars and molars narrower and more 
compressed, symphyseal region shallow and elongate, m+ more 
REMC OEE rl ear Tye AiG ones oa S. vulpecula. 
11. Mis = 17 mm.; premolars with slender acute cusps, a consider- 
able diastema, behind py. 03.40)... (a eee S. ?secundaria. 
12. Mi_3 = 18.7 mm.; heels larger than in the three preceding species. 
S. minor. 
13. M+? = 14 mm., smaller than any preceding...... S. viverrina. 
IV. Jaw heavy, symphyseal region massive, symphysis close, premolar construction 
approaching Limnocyonine. 
14. Mis = 21 mm.; ms; somewhat reduced...........__. S. mordax. 
