146 PSEUDOCERATITES OF THE CRETACEOUS. 
KNEMICERAS SyRIAcUM (von Buch). 
Pl. XVI, figs. 48. 
Amm. syriacus yon Buch, Abhandl. K. Akad. Wiss. zu Berlin, 1848, pl. 6. 
Knemiceras syriacum Bohm, 1898, Zeitschr. Deutsch. geol. Gesell., Vol. L, p. 200. 
Von Buch’s figures of this species on his pl. 6 are excellent in all 
characters, but his suture line on pl. 7 is either erroneous or belongs to 
another form. 
One gerontic specimen is about 55 mm. in whole diameter, with living 
chamber nearly one-half of a volution in length. A smaller specimen, 45 
mm. in diameter, has also reached into an extreme gerontic substage and 
has living chamber of same length. Von Buch’s specimen, according to 
his figures, was also in gerontic stage, but evidently somewhat larger, 
perhaps 70 mm., or thereabouts, when living chamber was present. 
This stage is indicated in one specimen as in von Buch’s figure by the 
approximation of septa in pairs as if the individual were only temporarily 
affected by weakness and then resumed the usual rate of increase. In one 
specimen the last sutures are irregularly spaced. The last three next to 
the living chamber are approximate. A slightly greater interval occurs 
between these, and there is a pair closely approximated, and apicad of this 
is a broader chamber and again a pair of approximated sutures. Apicad of 
this last pair there is a chamber broad on the venter but so narrow near the 
lines of involution that the sutures are crowded together on the umbilical 
shoulder. Apicad of this is the ephebic stage, with all sutures regularly 
spaced. The gerontic sutures are not always so irregular, and there may 
be as many as eight sutures showing more or less inequality in spacing, 
ending with a-series gradually becoming closer and eventually overlapping. 
The whole duration of the gerontic stage, including the living chamber, 
consists of about three-fourths of a volution. The lobes and saddles become 
shorter and the outlines simpler in this stage. Temporary approximation 
of sutures occurs often in the growth of these shells, and it is not always a 
sign that the gerontic stage has been reached, but when it is continued for 
some time, as in von Buch’s figure, and after a period of prolonged regu- 
larity in the width of the living chambers, it is obviously due to senility. 
There are no signs of a row of tubercles on the median aspect of the sides, 
and there are obviously only two rows of nodes with heavy fold-like bifurcated 
costee between. 
