20 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxix. 



ORTHOTHECA DAULIS, new species. 



Shell elongate, slender, tapering gradually to an acute point. 

 Transverse section subcircular, slightly flattened on the dorsal side. 

 Ventral face strongly and regularly convex transversely; the dorsal 

 and ventral faces meet to form the rounded lateral angles of the shell, 

 the dorsal face being narrow and slightly flattened. Aperture trans- 

 verse, as indicated by the transverse lines of growth. 



Surface of the shell smoothed and polished, with onlv a very few 

 obscure traces of transverse concentric lines of growth. 



The largest specimen in the collection has a length of 16 mm., with 

 a diameter at the larger end of 4 mm., and at the smaller end, where it 

 appears to be broken off at a transvei'se septum, of 1.25 mm. 



This species resembles, in its slender tube and nearly circular sec- 

 tion, OrtJiotheca communis Billings." It difl'ers in expanding a little 

 more rapidly toward the larger end and in its smooth surface. It may 

 be compared with ChthotJieca stylus Holm, except that it does not have 

 the curvature of that species nor the cancellated surface. Its slender 

 tube and nearly circular section are much like those of Orthotheca 

 tereti'usculus Linnarsson,^ as illustrated b}^ Holm in his memoir on 

 Hyolithida?. 



Formation and locality. — Middle Cambrian, lower portion of Chang 

 Hsia formation, in gray oolitic limestone; 50 feet below base of cliff's, 

 Chang Hsia; also central portion of Chang Hsia formation, 2.2 miles 

 southwest of Yen Chuang, Hsin Tai, Shangtung, China. 



Collected by Eliot Black welder, of the Carnegie Institution of 

 Washington Expedition to China. 



ORTHOTHECA DELPHUS, new species. 



Shell straight, elongate, slender, tapering gradually to an acute 

 point. Transverse section subelliptical, with the dorsal side flattened. 

 Dorsal face gentl}^ convex, lateral angles rounded. Ventral face 

 moderately convex. Aperture about transverse, as indicated by the 

 concentric stride and lines of growth. Shell of medium thickness. 



Surface of the shell transversely or concentrically striated by 

 somewhat irregular, raised, sharp, tine, closel}^ arranged stria^; on 

 the rounded ventral side a few slightly oblique, longitudinal, elevated 

 •lines occur near the larger end. 



The largest specimen has a length of J> mm., with a width of 1 mm. 

 at the smaller end and 1.75 mm. at the larger end. 



There is some variation in the transverse section of the shell owing 

 to the variation in the convexit}" and flattening of the dorsal face. In 

 some specimens toward the apical end the section is a rather narrow 

 ellipse. 



"Tenth Ann. Rept. U. S. Geol. Survey, 1890, pi. lxxvii, fi^s. 3, 3 a-g. 

 ''Geol. Surv. Sweden, Ser. C, No. 112, pi. i. 



