128 PSEUDOCERATITES OF THE CRETACEOUS. 
whitei. There are more of them, and only the last begin to reach entirely 
across the sides. ‘There is a sigmoidal channel on either side that does 
not reach across the venter. This is a characteristic occurring also in 
M. liardense, but not in other species. This occurs close to what must have 
been the edge of the aperture, since the living chamber is considerably 
over three-fourths of a volution in length and was probably a little longer 
when complete. The black line shows the position of the basal septum of 
the living chamber shown on the opposite side of the fossil figured. 
Locality: Elm Fork, Horton’s mill, Dallas County, Tex. 
Age: Colorado epoch. 
HEINZIIDZ. 
The members of this family are easily distinguishable from the typical 
Pulchelliide by the possession at some stage of elongated, usually 
double, but more or less connected tubercular terminations on the ventral 
ends of the lateral costee. All of the forms so far known have coarser and 
more complete lateral coste than are usual in Pulchelliidee, and there is, 
especially in primitive forms, a tendency to the development of stouter 
volutions, with less involution and consequently wider umbilici. The 
average size is larger, and the development is very distinct in all forms, so 
far as known. The young are stouter, less involute, and have costs con- 
tinuous across the venter. The tubercles appear upon these coste in two 
lines of single tubercles, and then subsequently two rows are developed 
upon the outer sides of these that remain more or less closely connected. 
The lateral coste are similar to those of Pulchelliidze, but sometimes a 
median or an inner row of tubereles or both appear in the later stages. 
The ventral channels are apt to be real channels furrowing both the coste 
and the intercostal spaces on the venter, and in the young and in primitive 
forms are apt to be narrow and smooth. The sutures are similar to those 
of Pulchelliidee, but as a rule have fewer and larger saddles and lobes, and 
the outlines more complex at the same comparative age, judging from the 
size of the casts. 
The development is so distinct from that of Pulchelliidze in some species 
of Heinzia that if it were not for the fortunate accident that placed one 
specimen of Heinzia matura in my way, I could not have offered any 
rational suggestion as to the true relations of this family. The development 
of Heinzia matura, however, shows, as stated below, a form that in the 
