23 



l886. Stiiiotliica rugvsa Walcotf ; Second Contribulion to tlie Studies 

 on the Cambrian Faunas of North America. P. ij8, pi. XII., tigs, 

 r a — e. 



1S90. Stoiothcca 1 nigvsa \\I KLCon : The Fauna of the Lower Cam- 

 brian or OliJiclhis Z(_->ne. P. 617, pi. LXXIV., figs, la-i, 2 — 7. 



1909. Hclcioiiclla nt,:;i>sa A. W. Grailvu and H. W. Siu.mek : North 

 American Index Fossils, Invertebrates. Vol. I., p., 607, tigs. Sio. 



1905. Sti'iiofhica n/ij'osa c/iinciisis M\d o)-u-ntalls Wai.coit: Cambrian 

 P^auna of China, p. 16. 



191 3. Hi-lciouclla riig'osa cliiuctisis lXW^. oriiiitalis Wai.cO'it : The Cam- 

 brian P'auna of China. P. qi, pi. V., tigs. 8, 15, 15a. 



Shell capuliform, depressed conical, aperture elliptical, apex produced 

 and acute, submarginal and incurved. Concentric folds broad, becoming 

 gradually obsolete toward the aperture. 



Dimensions : — The largest specimen has a height of 3.8 mm. and an aper- 

 ture of 3 mm. in l<Migitudinal diameter. 



This species, //. riiiiosa, is very variable in form antl sculpture ; the pre- 

 sent form much resembles H. rugvsa pauf'cra Bili.ixgs.^^ Of the two forms 

 of this species described by WAr.corr from China, /./. rn^^'osa cliinciisis 

 has a less incurvetl shell with more numerous and narrower folds ; H. rugvsa 

 oricutalis., on the other hand, differs considerably from the present form by 

 having a strikingly prolonged shell with acute folds. //. rugosa /HXiipcra is 

 known from the Lower Cambrian of Newfoundland and eastern Massachussetts. 



\.oc. : — Ta-shi-tou, I lui-tso-hsien, prov. Yun-nan ; found together with 

 Orthotlieca giahra WAr.coTT in dark grey earth}' limestone. 



H. rugosa f/iiiicasis is found in the lower part of the Man-to shale forma- 

 tion (Lower Cambrian) ofShan-tung, while H. ?-iigvsa oriental is is known from 

 the middle part of the Chang-hsi fo rmation ( Aliddle Cambrian) 01 Shan-tung. 



Geological Age : — Cambrian, in all probability Aliddle Cambrian. 



i) Walcoit: Second Contribution, p. 129. " O^i exAm'nin:^ tlie type of Stenotheca panfera 

 in the collection of the Geological Survey, I found it to be a coarsely ribbed variety of 

 .S". r 1 1. JO' a." 



/ 



