58 SMITHSONIAN* MISCELLANEOUS COLLECTIONS VOL. IO3 



BYNUMIELLA (?) OKLAHOMENSIS, new species 

 Plate 10, Figures 27, 28 



Pending the availability of better material several .cranidia that are 

 not fully typical are referred to the genus. This species differs from 

 typical forms in that the glabella tapers less rapidly and in the size 

 and position of the eyes, which are far larger and situated much 

 farther back than they should be for a Bynumiella. Brim, occipital 

 ring, and fixigenes are all typical. 



The illustrations show the characteristics of the holotype cranidium. 

 Faint glabellar furrows are present. A thickening of the neck ring 

 produces a short blunt spine. Longitudinal curvature is shown in 

 figure 27, and that in the opposite direction is about the same. 



Signal Mountain formation; (loc. 201 j) i mile south of Royer 

 Ranch, Arbuckle Mountains, Oklahoma. 



Holotype.— IJ. S.N. M. No. 108743. 



BYNUMINA, new genus 



A second genus Bymunina is erected for the Bynumia stock that 

 continued into Franconia time. As in Bymimiella this genus represents 

 development of Bynumia in the direction of more average trilobite 

 structure. Although glabellar taper was an essential change in this 

 instance, the head as a whole is less constricted anteriorly. Glabellar 

 furrows also appear, but the most pronounced change lies in the brim 

 structure, which brings that part more nearly to form a transverse 

 band. 



Diagnosis. — Small trilobites characterized by large, somewhat ta- 

 pered glabella. Dorsal and occipital furrows well defined. Glabellar 

 furrows faint. Neck ring narrow and of even width throughout. Eyes 

 small, situated well forward. Brim simple, of nearly even width 

 throughout. Faint eye lines present. Pygidium simple ; axis long, 

 tapered, poorly defined, and with faint axial rings. Pleural lobes 

 completely fused. 



Genotype. — B. eaelata. new species. 



BYNUMINA CAELATA, new species 



Plate 10, Figures 18-22 



Numerous cranidia and one pygidium represent this species. The 

 illustrations show both the generic and specific characteristics. 



The glabella tapers gradually to a truncated front margin. The 

 anterior corners are rounded, and along the sides the dorsal furrow 



