716 GEOLOGICAL SURVEY OF IOWA. 



Dolabra ? alpina ( n. s.). 



PLATE XXIX. Fia. 2. 



SHELL subrhomboidal ; length a little greater than the 

 height ; anterior extremity rounded ; posterior extremity 

 obliquely truncate ; umbo gibbous ; the beak elevated, near- 

 ly central ; an obtuse ridge extending from the beak to the 

 posterior basal margin, and the space between this and the 

 margin somewhat concave, 



SURFACE marked by fine concentric stride, and, near the 

 margin, by stronger imbricating lines of growth. 



This shell has the external form of some of the characteristic species of the Genus 

 DOLABBA of M'Cor; but I have not been able to ascertain the structure of the hinge. 

 Fig. 2. View of the left valve, natural size. 



Geological formation and locality. In the Lower Coal measures of the 

 Desmoines valley, Alpine darn, Iowa. 



Edmondia ! radiata ( n. s.). 



PLATE XXIX. FIG. 3. 



SHELL oval-ovoid ; length much greater than the height ; 

 beak near the anterior extremity, slightly sinuate on the 

 anterior basal margin ; posterior extremity broadly rounded ; 

 anterior extremity rounded below, and concave just beneath 

 the beak. 



SURFACE marked by concentric and radiating striae, the 

 latter somewhat more conspicuous when the shell is partially 

 exfoliated. 



This species is described from a single well-marked right valve. 



Fig. 3. View of the right valve, from which the shell is partially exfoliated. 

 Geological formation. Coal measures. 



Nucula ventricosa ( n. s.). 



PLATE XXIX. Fia. 4 & 5 a, b. 



SHELL ovoid, gibbous or subventricose on the middle and 

 upper part of the shell ; outline regularly curving to the 

 base and posterior extremity : beaks near the anterior ex- 

 tremity incurved and inclining forwards, with a cordiform 

 depression beneath them. 



