KNEMICERATID&#. 149 
and in the presence of these incrusting growths on the casts for consid- 
ering them as having been fossil casts when the incrusting animals erew 
upon them. 
Locality: Mount Lebanon, Syria. 
Age: Cenomanian. 
KNEMICERAS COMPRESSUM n. sp. Hyatt. 
Pl. XVI, figs. 9, 10, 15-18. 
Ammonites vibrayeanus Hamlin, 1884, Mem. Mus. Comp. Zool., Vol. X, No. 3, p. 12. 
The typical form of this species is separable from the variety 
subcompressum in full-grown specimens by the greater compression of the 
volutions, narrower venter, and less development of the nodes on the 
umbilical shoulders. The proportionate increase by growth of the ventro- 
dorsal diameters is also greater with relation to the transverse than in the 
stouter variety described below, and in all these respects it differs still more 
from Knem. syriacum. he shell, however, until 45 to 50 mm. in diameter 
is not distinguishable from the shell of that species. As stated by Fraas and 
Hamlin, the sutures in the worn casts are similar to syriacum, but in a large 
specimen of the same size as the type of this species (Pl. XVI, fig. 15) in 
the Museum of Comparative Zoology these are less worn than usual and 
full grown. These sutures (Pl. XVI, figs. 17, 18) show the large ventral 
lobes, which occupy nearly the entire breadth of the venter instead of only 
the central part, as in the stouter variety and in syriacum. The lateral 
saddles and lobes are very long and narrow and the bases of the saddles 
swollen, rounded, and phylliform, resembling those of Sphenodiscus. The 
apical ends of the saddles are also similarly shaped, broad, denticulated, 
and cutting deeply into the saddles. In the gerontic stage the lobes and 
saddles become shorter again, as in the younger stages, and more like those 
of syriacum. The most perfect cast (Pl. XVI, figs. 15, 16) is 70 mm. in 
diameter, without living chamber, the outer volution 38 mm., the umbilicus 
10 mm., and same volution opposite 22 mm., the thickness of the last being 
13 mm. between coste. 
The largest specimen is from Beirut, No. 10902G in the collection of 
Columbia University. This has no living chamber, and the actual 
diameter is 85 mm., estimated diameter about 90 mm. Diameter when 
living chamber was present could not have been Jess than 1380 mm. 
