76 
Kirtley F. Mather 
range east of the Mississippi River, ranges from Stage B to 
Stage G in Kansas, and is known from the Cordilleran region 
as well. It has, also, been reported in the Waverly formations 
of Tennessee and in the Marshall of Michigan. 
Parallelodon sangamonensis is a typical mid-Pennsylvanian 
pelecypod occurring in the Mercer and Brush Creek limestones, 
the Coal Measures of Illinois and Missouri, and ranging in Kan- 
sas from Stage C to F. It is accompanied in the Morrow by 
two new species of the same genus whose affinities with forms 
in either higher or lower horizons are not marked. Cypricar- 
dinia is represented by a new form with similar indefinite affin- 
ities. 
The Myalmas are numerically the most important pelecypods 
of the fauna. M. cuneiformis is known elsewhere only from 
Pennsylvanian limestones of Colorado, M. orthonotis is a new 
species, and M. recurvirostris is frequently found in the Coal 
Measures of the central states, ranging from Stage D to F of 
the Kansas section. Schizodus, a genus which although present 
in all Carboniferous horizons is most abundant in Permian for- 
mations, is represented by a new species. 
The pectens are an essential element of the pelecypod fauna 
of the Morrow, as is usually the case in Carboniferous faunas. 
In addition to several new species, four well-known ones have 
been identified. Aviculopecten hertzeri and A.? interlineatus are 
typical Pennsylvanian types recognized in the Cordilleran as 
well as the interior provinces. A. talboti, on the contrary, is a 
Ste. Genevieve limestone form with which the Morrow individ- 
uals are closely related if not conspecific. Deltopecten occiderr- 
tails has a wide distribution and long range in the Pennsyl- 
vanian terranes of this continent. 
Monopteria and Pseudomonotis are not known to occur below 
the Pennsylvanian in North America. The former is doubt- 
fully represented by a fragmentary individual in the Morrow 
while to the latter genus are referred two new species. Another 
undescribed form is referred to Paleolima, a genus fairly abun- 
dant in the Carboniferous of England. Pleurophorus tropi- 
dopherus is a typical Pennsylvanian form which ranges from 
Stage C to H of the Kansas section and occurs in the Mercer 
of Ohio as well as in the Coal Measures of Missouri. 
