28 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 134 
is apparent, that of the Oregon genus being much more strongly 
developed. 
The external ornamentation of Marginifera with its strong costel- 
lae on a long trail, strongly sulcate trail, and rugose visceral disk is 
like that of Probolionia. A major difference on the exterior appears 
in the strong row of spines on the flanks of Marginifera which ex- 
tend from the anterior margin nearly to the beak and overhang the 
naked ears. On the inside another difference between the two genera 
is apparent. The marginal shelf in Marginifera is an overhanging 
ledge as it is in Probolionia but it does not bear a series of trails as 
in the Oregon genus (text fig. 2C). The shelf in Marginifera appears 
to have been built out from the visceral disk but no additional trail 
added; the shelf thus forms a ledge over the trail rather than being 
the trail attachment of the brachial valve. 
> 
SSS 
A G D 
Fic. 2.—Longitudinal sections of productoid genera. 
| 
. Probolionia posteroreticulata Cooper, new species. Longitudinal section showing the 
diaphragm and numerous trails of the pedicle valve, & 2, paratype, U.S.N.M. 125366e. 
Compare with figures C and D. Locality S103. 
. Proboscidella? carinata Muir-Wood and Cooper, new species. Longitudinal section showing 
the thickened subperipheral rim on the pedicle valve, 2.5, hypotype, U.S.N.M. 126081a. 
Locality 2204-1. 
. Marginifera typica Waagen. Longitudinal section showing margin on brachial valve and 
lack of trails on exterior of that valve, X 2, hypotype, U.S.N.M. 124032b. ; 
Permian, + mile southeast of Fazawadi Dhok, above Warcha Mandi, Salt Range, Pakistan. 
. Diaphragmus cestriensis (Worthen). Longitudinal section showing diaphragm and trails on 
brachial valve, * 2.25, hypotype, U.S.N.M. 124040. : 
Fayetteville formation 4 mile south of Glendale School, just east of east line of sec. 20, T. 15 
N., R. 20 E., Muskogee County, Oklahoma. 
No other genus having a shelf in the brachial valve like Margim- 
fera appears to be related to the Oregon genus more than in a family 
relationship. Eomarginifera has spines like Probolionia but the 
ornamentation and marginal ridge are quite different. Spinomargini- 
fera has a different arrangement to the spines, and Paramarginifera 
is differently ornamented, is transverse, and has a strong marginal 
ridge in the pedicle valve. 
