SCAPHOPODA—DENTALIIDJE. 



579 



Smooth, rather rapidly expanding, moderately curved ; section 

 circular, growth lines arching forward on concave side. 

 Columbus limestone of Ohio. 



2. D. (Laevidentalium) pauperculum M. & H. (Fig. 795, a.) 



Cretacic. 

 Minute, smooth, gently curved, gradually tapering, section cir- 

 cular, shell thick, lines of growth oblique. 



Pierre and Fox Hills of upper Missouri river region. 



3. D. gracile Hall and Meek. (Fig. 795, d-d.) Cretacic. 

 Very gently tapering and slightly curved, section nearly or 



quite circular ; apical end smooth ; fine round longitudinal lines 



i 



o 



Fig. 795. a, Dentalium paupercuhim, 

 natural size ; l>-d, Dentalium gracile ; b, 

 part of shell ; c, enlargement of surface ; 

 d, section of large end, (After Meek.) 



Fig. 796. 



Dentalium 



stramineum. 



(After Gabb. 



Fig. 794. 

 Dentalium 

 martini. 

 (After Whit- 

 field. ) 



over most of shell, increased by intercalation and becoming obsolete 

 toward larger end. 



Pierre formation of Dakota and the Yellowstone river region. 



4. D. stramineum Gabb. (Fig. 796.) Cretacic. 

 Rather rapidly tapering, slightly curved, and with numerous 



longitudinal lines or ridges. 

 Upper Cretacic of California. 



5. D. (Antalis) cooperi Gabb. (Fig. 797.) Cretacic. 

 Very gently curved, moderately tapering, surface with numerous 



fine parallel striae separated by depressed lines. 

 Upper Cretacic of California and Sucia Island. 



6. D. subarcuatum Conrad. Cretacic. 

 Slender, very gently arcuate, tapering in 47 mm. from 5 mm. 



