DESCRIPTION OF GENERA AND SPECIES. 



Order ATREMATA Beecher. 



[a, without; and zprnmj perforation.] 



Superfamily EUSTELLACEA Walcott. 

 Family RUSTELLID^ Walcott. 



Genus BXJSTEIiLA Walcott.a 



Rustella Walcott, 1905, Proc. IT. S. Nat. Mus., vol. 28, p. 311. (Mentioned as a new genus, the type species being 



described.) 

 Rustella Walcott, 1908, Smithsonian Misc. Coll., vol. 53, No. 4, PL XI, and pp. 142 and 143. (Classification of genus.) 



This genus is founded on Rustella edsoni Walcott. It appears to be the most primitive 

 form of brachiopod known. The single specimen of Rustella .? major (Matthew) does not add 

 to our knowledge of this genus, and it may belong to some other genus. 



The generic name is given in memory of WUliam P. Rust, of Trenton Falls, Oneida County, 

 New York, whose collections from the Lower Cambrian strata of Georgia, Franklin County, 

 Vermont, were the most extensive and the material the finest obtained there, so far as known 

 to me. 



Rustella edsoni Walcott. 



Plate 1, figures 1, la-e. 



Oholella (Kutorgina) cingulata Billings (in part), 1861, Geol. Survey Canada, Paleozoic Fossils, vol. 1, p. 8, fig. 9 (not 



figs. 8 and 10, which represent specimens of the true Kutorgina cingulata). (Described and discussed as a new 



species.) 

 Oholella {Kutorgina) cingulata Billings (in part), 1861, Report on the Geology of Vermont, vol. 2, p. 948, fig. 348 (not 



figs. 347 and 349). (Copy of preceding reference.) 

 Oholella {Kutorgina) cingulata Billings (in part), 1862, Report on the Economic Geology of Vermont, by Hager, p. 220, 



fig. 348 (not figs. 347 and 349). (Copy of preceding reference.) 

 Oholella cingulata Billings, 1863, Geol. Survey Canada, Fifteenth Rept. Progress, p. 284, fig. 287c (not figs. 287a and 



287b, which represent specimens of the true Kutorgina cingulata and are copied from Billings, 1861b, p. 8, figs. 



8 and 10, respectively). (No text reference. Fig. 287c is copied from Billings, 1861b, p. 8, fig. 9.) 

 Kutorgina cingulata Walcott (in part) [not (Billings)], 1886, Bull. U. S. Geol. Survey No. 30, p. 103, PI. IX, figs. Ig 



and Ih (not figs. 1, la-f, which represent specimens of the true Kutorgina cingulata). (Specimens now referred 



to Rustella edsoni are here mentioned in the discussion of Kutorgina cingulata as representing a possible distinct 



species. The specimens represented by figs. Ig and Ih are redrawn in this monograph, PL I, figs, la and 1, 



respectively.) 

 Kutorgina cingulata Walcott (in part) [not (Billings)], 1891, Tenth Ann. Rept. U. S. Geol. Survey, p. 609, PL LXIX, 



figs. Ig and Ih (not figs. 1, la-f, which represent specimens of the true Kutorgina cingulata). (No text reference. 



Figs. Ig and Ih are copied from figs. Ig and Ih of the preceding reference.) 

 Rustella edsoni Walcott, 1905, Proc. U. S. Nat. Mus., vol. 28, pp. 311-312. (Described and discussed as below as a 



new species.) 



General form subcircular, biconvex. Ventral valve moderately convex, with the apex at 

 the margin immediately above a low arch in the posterior margin. Surface smooth except for 

 concentric growth lines and low ridges that in some shells are quite promment. A shallow, 

 broad, rudimentary pedicle groove occurs beneath the apex and on a slightly flattened space 

 adjoining the posterior margin. Dorsal valve about as convex as the ventral and with the apex 

 marginal. The interior of the valve shows two rounded depressions beneath the umbo with a 

 slight, narrow groove between them; a Uttle in advance the outlines of the central muscle 

 scars occur; rather strong but faintly indicated radiating lines occur toward the front. 



a Before Rustella was proposed by Walcott [1905a, p. 311] the species now included under the genus were placed in the following genera: 



ObofcZraCffiifoi-yiTja) Billings [1861b, p. 8; 1861c, p. 



948; 1862e, p. 220]. 

 ObolelU BiUings [1863, p. 284). 

 Kutorgina Walcott [1886b, p. 103]. 



Oiolus Matthew [1890, p. 155]. 

 Kutorgina Walcott [lS91a, p. 609]. 

 Mickwitzia Mickwitz [1896, p. 23]. 



