332 CAMBRIAN BRACHIOPODA. 



in Mickwitzia pretiosa Walcott. The outline of the valves appears to have been ovate to sub- 

 circular and the ventral valve rnoderately convex. The shell is phosphatic or chitinous and 

 built up of three principal layers. The outer layer is thin, and thickly set with minute pustules 

 or granules that give the surface a roughened appearance. When the outer layer is exfoliated, 

 which is usually the case, the aniddle layer presents a smooth, shining surface that is marked 

 by a few concentric striae and numerous fine radiating striae, between which many minute punctae 

 occur. The inner layer shows niinute, irregular, serpentine, rounded ridges, perforated by 

 vertical canals or punctas. An interior of a ventral valve shows the lines of advance of the 

 anterolateral muscle scars. The largest shell indicated on the surface of the siliceous shale 

 has a length and width of 12 mm. 



The generic reference of this species is based on the apex of the ventral valve and the 

 structure and character of the shell. 



Formation and locality. — lower Cambrian : (53) Sandstones in the lower portion of 3d of the Waucoba Springs 

 section [Walcott, 1908f, pp. 187 and 188|, 1 mile (1.6 km.) east of the Saline Valley road, about 2.5 miles (4 km.) east- 

 northeast of Waucoba Springs, Inyo County, California. 



(174c) Sandstones on small hill in the salt flat, 1 mile {1.6 km.) northeast of Silver Peak Mill, Silver Peak quad- 

 rangle { U. S. Geol. Survey), Esmeralda County, Nevada. 



Mickwitzia pretiosa Walcott. 

 Plate VI, figure 2. " 



Mickwitzia pretiosa Walcott, 1908, Smithsonian Misc. Coll., vol. 53, No. 8, pp. 54-55, PI. VII, fig. 2. (Described and 

 discussed as below as a new species. Fig. 2 is copied in this monograph, PL VI, fig. 2.) 



This species is founded on a single specimen of a ventral valve. It has a length of 7 mm., 

 width 6.5 mm. Outlhie subcircular, slightly convex; apex curved over toward the posterior 

 margin and projecting beyond it. False area short and obscure. Surface marked by radiating 

 raised lines that at the front margin show six in a distance of 2 millimeters. Fine papillae are 

 thickly scattered over the surface, with a tendency to follow concentric lines of growth on some , 

 portions of the shell, and on others they appear on low, narrow, serpentine ridges, as in M. 

 momZt/era (Linnarsson). A few large punctae are scattered here and there over the surface. 

 Inner surfaces and layers of shell unknown. 



This beautiful shell differs in the details of its surface from M. monilifera; it is also less 

 convex, and the apex is nearer the posterior margin. 



FoKMATiON AND LOCALITY. — Lower Cambrian: (390j) Eophyton sandstone at Lugniis, 8 miles (12.8 km.) south- 

 southwest of Mariestad, Province of Skaraborg, Sweden. 



Mickwitzia ? sp. undt. 

 Lingula hawkeif Bornemann [not Rouault], 1891, Nova Acta Acad. Cses. Leop. -Carol. Germanicse Natures Curiosorum, 

 Bd. 56, No. 3, p. 439, PI. XIX, figs. 19-20. (Characterized and discussed in German.) 



Bornemann describes and illustrates some large shells 3 centimeters or more in diameter 

 from the Olenopsis beds, which he states are characterized by a somewhat quadrangular outHne 

 and faint sinus and resemble Barrande's "Lingula feistmanteli." I am inclined to compare 

 this form with the large compressed casts of Mickwitzia monilifera and to make a tentative 

 reference to the genus Mickwitzia. The shell is certainly not Lingula rouaulti Salter. 



Formation and locality. — Middle? Cambrian: (354a [Bornemann, 1891, p. 439]) in grayish-white quartzitic 

 sandstones in the valley of Gutturu Sartu, island of Sardinia, Italy. 



Genus MICBOMITBA Meek.o 



[/MKpdc, small; and mitra, a hat.] 

 Not Iphidea Baly, 1865, Entom. Monthly Magazine, vol. 2, p. 127. (Proposed for a genus of Coleoptera.) 

 Iphidea Billings [not Baly], 1872, Canadian Naturalist, 2d ser., vol. 6, No. 4, pp. 477^78. (Type species ("Iphidea 

 bella " ) described and discussed and ' ' Iphidea " mentioned as a new genus. The reference is copied in this mono- 

 graph under Micromitra (Paterina) bella, p. 345.) 



a The synonymy for this genus does not give a complete record of the various genera under which the species now included in Micromitra were 

 formerly placed; it includes only those references in which the genus is discussed or described. Por the sake of completing the record the remaining 

 mere generic references are here listed: 



Eutorgina Linnarsson [1876, p. 25]. I Kutorgina Matley [1902, p. 146]. 



Kutorgina Hall and Whitfield [1877, p. 207]. Eutorgina Gronwall [1902, p. 40). 



Kutorgina Walcott [1884b, p. 20). I 



