ENGONOCERATID.®. 181 
venter in the neanic stage, and were obviously similar to Protengonoceras in 
their young. The smaller fragment, nearly one-half of a volution, with 
center partly preserved, is 52 mm. in diameter, and the venter is worn, but 
in places where sutures are perfect the venter is narrowly rounded. In the 
largest cast, at about the same age, I was able to demonstrate by excava- 
tion that the shell, although very narrow, was thick and distinctly concave 
on the venter. There were apparently no large tubercles at any stage. 
The first lateral saddles in the small fragment, at a diameter of over 52 mm., 
were broad, very short, and had the inner angle furnished with a large 
marginal lobe and saddle. 
The second to fifth saddles on the right side, and the second to sixth 
on the left side, are entire, the sixth on the right and seventh on the left 
being the first of the bifid saddles. The other saddles are all bifid, except, 
perhaps, the innermost pair, but this was not seen. 
The lobes are too much worn down to show their minute digitations 
except in a general way. ‘The ventral lobe and minute median saddle are 
present and the first lateral saddles are narrow. On the youngest and 
least-worn part of the larger specimen on the right side, the first lateral 
saddles show slight marginal lobes and saddles at each of the inner angles, 
but there are minute marginal lobes on the outer parts of these saddles. 
Several of them show this division, and one is distinctly tritid. On the 
older parts of the same specimen they are, however, distinctly entire as in 
the other fragment, and this I think is the normal character. The wearing 
to which it had been exposed caused me at first to count three entire 
saddles on the left side and four on the older parts of the same volution. 
It is obvious, however, that it is the sixth saddles that are bifid on both 
sides. The remaining saddles are bifid to the line of involution. In both 
of these specimens there are ten saddles and nine lobes, but there was 
probably in each a lobe on the line of involution. The youngest sutures 
were about 5 mm. distant, but the last nine lost distance rapidly and were 
more or less irregular, and in the last four the second lateral saddles 
overlapped slightly the second lateral lobes. 
The larger cast has three much-worn fragments of the attached valves 
of an ostrean on the right side, which had evidently been exposed above 
the calcareous mud while in the same condition as at present, namely, a 
distorted fossil cast, and the ostreans grew upon the surface of the cast, 
itself. That the cast had already suffered from attrition and compression 
