NO. 1-1:5. CAMBRIAN FAUNAS OF CHINA— WALCOTT. 17 



PTEROPODA. 



Genus HYOLITHES Eichwald. 

 HYOLITHES CYBELE, new species. 



Form an elong-ate, ,su])ti'iano-ular pyramid, oracliuiliy and rooularly 

 taperiiig to an acute extremity. The apical angle of the dorsal side is 

 about 15-^. Transverse section rounded subtriang'ular; the ventral 

 angle is rounded and the lateral angles slightl}' rounded olf. Dorsal 

 face moderately convex and curving very slightly from the apex to 

 the anterior, spatulate portion. Ventral face strongly and regularly 

 convex transversely. Aperture oblique, the margin extending- on 

 the dorsal side; the peristome 'on the ventral side is slightly curved 

 forward. 



Surface marked b}" concentric, transverse, more or less o])scure lines 

 and striiB of g-rowth; the cast of the interior shows on the ventral face 

 three or four obscure longitudinal lines, the central one of which is 

 the strongest. 



The largest specimen in the collection has a length of 24 nmi., with 

 a width of T mm. at the aperture. 



The body of the associated operculum is semicircular, moderately 

 convex on the outer side externally, and concave within. The ventral 

 wing as seen on the outside is semicircular-convex, rising toward a 

 point at the center of the transverse side. The dorsal limb is nearly 

 flat, rising, as far as can be determined from a broken specimen, at an 

 angle of about 100^ from the plane of the body of the operculum. 



In the slope of the sides toward the apex, character of surface, and 

 the transverse section this species may be compared with IfyoJitJi<x 

 pr'rnccp^!^ Billings," of the Lower Cambrian of Newfoundland, //. tenah- 

 ti'hitus Linnai'sson, and //. arcnophllus Holm.^^ If. ri/hdexs^ however, 

 much smaller than the first two species mentioned, and its section is 

 much more convex, both on the dorsal and ventral sides, than that of 

 // arenopldlux.. 



Forniiitkm.andlocalitii. — Middle Cambrian, central poi'tlon of Chang 

 Hsia formation; at Yen Chuang, 2 miles and 2. .5 miles south and 3 

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

 near the top of the Chang Ilsia formation at Chang Ilsia, Shangtung, 

 China. 



Collected l)y Eliot Blackwelder, of the Carnegie Institution of 

 Washington Expedition to China. 



"Tenth Ann. Kept. U. S. Geol. Survey, 1890, pi. lxxvi, fit^s. 1 to 1 '//. 

 'Mieol. Surv. Sweden, Ser. C, No. 112, pi. i, tigs. 78-81 and 8LM>;!. 



Proc. N. M. vol. xxix— 05-^ — 2 



