802 CAMBRIAN BRACHIOPODA. 



Observations. — The young shells of this species are almost evenly convex, the fold of the 

 dorsal valve and the sinus of the ventral valve of the adult shell not having developed. The 

 characteristic spondylium of each valve is shown in the youngest shells observed. The general 

 form of Syntropliia campielli is much like that of SyntropMa rotundata Walcott (PI. GUI, figs. 



4, 4a-c) and somewhat like that of Huenella texana (Walcott) (PI. CIII, figs. 1, la-g). It 

 differs from the former in having the spondylium of the dorsal valve resting on the interior of 

 the shell and not supported on a septum, in this respect resembling the spondylium of Huenella 

 texana (Walcott) (PI. CIII, figs. Ih, li). Some shells have a somewhat transverse posterior 

 margin like that of H. texana, but the larger number have the broadly acuminate outline of 



5. rotundata. The muscle scars of the dorsal valve, as far as known, are similar to those of 

 Huenella ahnormis (Walcott) (PL CIII, figs. 2i, 2s). 



The specific name was given in honor of Mr. M. R. Campbell of the United States Geological 

 Survey, who collected the specimens. 



FoEMATioN AND LOCALITY. — TTpper Cambrian: (12c() Knox dolomite, on Bunker Hill, 6 miles (9.6 km.) northeast 

 of Rogersville [Keith, 1905, areal geology sheet], Hawkins County, Tennessee. 



1 Synteophia lateralis (Wliitfield). 



V 



Text figure 11, page 299; Plate CII, figm-es 6, 6a-g. 



Triplesia lateralis Whitfield, 1886, Bull. Am. Mus. Nat. Hist. No. 8, p. 303, PI. XXIV, figs. 9-11. (Described as 



a new species.) 

 SyntropMa lateralis (Whitfield), Hall and Clarke, 1892, Nat. Hist. New York, Paleontology, vol. 8, pt. 1, footnote, 



p. 270. (Generic reference changed.) 

 SyntropMa lateralis (\^'hitfield), Hall and Clarke, 1893, idem, vol. 8, pt. 2, p. 217, PI. LXII, figs. 1-10. (Described, 



giving on p. 216 the footnote referred to in the preceding reference. The description of this species is copied 



in this monograph, under the genus SyntropMa. ' Figs. 9 and 10 ai-e copied in this monograph, PI. CII, figs. 



6f and 6g, respectively.) 

 SyntropMa lateralis C^^Tiitfield), Hall and Clarke, 1894, Thirteenth Ann. Rept. State Geologist New York for 1893, 



vol. 2, pp. 836-837, PL XLV, figs. 7-12. (Copy of the description given on p. 217 of the preceding reference. 



Figs. 7-12 are copied from Hall and Clarke, 1893b, PI. LXII, figs. 1, 2, 6, 9, 5, and 10, respectively.) 



I have illustrated a few of the shells representing the species that, taken with those of 

 Hall and Clarke in part 2 of volume 8 of their great work, illustrate about all that is known 

 of S. lateralis. (See p. 798 for a copy of Hall and Clarke's description of the species.) 



Formation and locality. — Lower Ordovician: (227) Limestone near Fort Cassin, Addison County, Vermont. 



Syntrophia nundina Walcott. 



Plate CII, figures 4, 4a-d. 



Triplesia calcifera Walcott [not Billings], 1884, Men. U. S. Geol. Sm-vey, vol. 8, pp. 75-76, PL XI, figs. 7 and 8. 

 (Chai'acterized. The specimens represented by figs. 7 and 8 are redrawn in this monograph, PL CII, figs. 4 

 and 4a, respectively.) 

 SrjntropMa nundina Walcott, 1905, Proc. U. S. Nat. Mus., vol. 28, p. 292. (Characterized as below as a new species.) 

 SyntropMa calcifera Walcott, Ghabau and Shimer, 1907, North American Index Fossils, vol. 1, p. 271, figs. 325. (De- 

 scribed. The two figures in fig. 325 are copied from Walcott, 1884b, PL XI, figs. 7 and 8, respectively.) 



The nonplicats, convex species that is found in the Lower Ordovician of the western 

 United States has usually been referred to Camerella or Triplesia calcifera. It is much like 

 the latter but differs in being less convex, with apex of valves less pointed and incurved. 



Formation and locality. — Lower Ordoviciaii: Pogonip limestone at the following localities: (63) Northeast of 

 Adams Hill; (201a) east slope of the ridge east of Hamburg Ridge; (203) on spur on ridge extending southwest from 

 Wood Cone; (204) on the lower part of the eastern slope of the ridge east of Hamburg Ridge, facing Secret Canyon road; 

 and (209) on the west side of Goodwin Canyon; all in the Eureka district [Hague, 1892, Atlas], Eureka County, Nevada. 



(185z) Limestones at the base of the Lower Ordovician [Walcott, 1908f, p. 191], in Blacksmith Fork Canyon, 

 about 9 miles (14.4 km.) east of Hyrum, Cache County, Utah. 



(186 and 186a) Near line of contact between red and gray Ordovician limestone, in red siliceous limestone, 30 

 to 35 feet (9.1 to 10.7 m.) above the pre-Cambrian rocks, Williams Canyon, Manitou, El Paso County, Colorado. 



Tipper Cambrian: (54b) About 1,200 feet (365.8 m.) above the Middle Cambrian and 25 feet (7.6 m.) below the 

 top of the Upper Cambrian in the upper part of the limestone forming 1 of the St. Charles formation [Walcott, 1908f, 



