424 CAMBRIAN BEACHIOPODA. 



somewhat obtuse angle. The surface is not well preserved in any specimen; judging, however, from some small frag- 

 ments, I should think that a concentric striation is prevailing, but that there are also radiating ribs. In the inner 

 shell layers little more than a longitudinal striation is seen; the innermost are perforated by small punctiform pits. 

 The inner layers are polished and glossy; the outermost seems to be opaque. 



Formation and locality. — Middle Cambrian: (3201 [Linnarsson, 1876, p. 16]) Drift blocks supposed to have come 

 from the Paradoxides xlandicus zone [lannarsson, 1876, p. 6], at Lillviken, near Oestersund, Province of Jemtland, 

 Sweden. 



BBOGGEBIA Walcott," subgenus of OBOLXTS. 



Obohis {Broggeria) Walcott, 1902, Proc. U. S. Nat. Mus., vol. 25, p. 605. (Characterized as below as a new subgenus.) 

 Obolus (Broggeria) Walcott, 1908, Smithsonian Misc. Coll., vol. 53, No. 4, PI. XI, and pp. 142 and 144. (Classification 

 of genus.) 



This subgenus differs from the typical forms of Oholus in having a very deep visceral 

 depression in both valves and a minutely punctate interior surface. A series of shells showing 

 the effect of compression on the appearance of the interior casts of the valves is illustrated on 

 Plate XIII. 



Type. — Oiolella salteri Holl. 



The generic name was given in honor of Dr. W. C. Brogger. 



Obolus (Broggeria) salteri (Holl). 



l_ 



Plate XIII, figures 1, la-n; Plate XV, figures 4, 4a-d. 



Obolella salteri Holl, 1865, Quart. Jour. Geol. Soc. London, vol. 21, pt. 1, p. 102, figs. 9a-b. (Described as a new 

 species; see below for copy. Figs. 9a-b are copied in this monograph, PL XV, fig. 4.) 



Obolella salteri Holl?, Davidson, 1866, British Fossil Brachiopoda, vol. 3, pt. 7, No. 1, pp. 61-62, PL IV, figs. 28 and 

 29. (Original description, Holl, 1865, p. 102, copied and species discussed. Fig. 28 is copied from Holl, 1865, 

 figs, 9a-b.) 



Obolella? salteri Holl, Davidson, 1868, Geol. Mag., vol. 5, p. 311, PL XVI, figs. 8-9. (Discussed.) 



Oboljis f salteri (Holl), Dall, 1870, Am. Jour. Conchology, 2d ser., vol. 6, pt. 2, p. 163. (Discussed.) 



Obolella salteri Holl, Phillips, 1871, Geology of Oxford and the Valley of the Thames, p. 68, Diagram XVII, fig. 11. 

 (No text references.) 



Obolus salteri (Holl^, Brogger, 1882, Die silurischen Etagen 2 und 3, pp. 44-45, PL X, figs. 10, 11, and 13. (Localities 

 mentioned in German. The specimen represented by fig. 10 is redrawn in this monograph, PL XIII, fig. Im.) 



Obolus f salteri (Holl), Mickwitz, 1896, M6m. Acad. imp. sci. St.-P6tersbourg, 8th ser., vol. 4, No. 2, p. 19. (Discussed 

 in German.) 



Obolella (?) salteri Holl, Matlet, 1902, Quart. Jour. Geol. Soc. London, vol. 58, pt. 1, pp. 139-140, figs. 3-6, p. 138. 

 (Described and discussed.) 



Obolus (Broggeria) salteri (Holl), Walcott, 1902, Proc. U. S. Nat. Mus., vol. 25, pp. 605-606. (Original description, 

 Holl, 1865, p. 102, copied as below, and species discussed essentially as below.) 



Obolus (Broggeria) salteri (Holl), Moberg and Segerberg, 1906, Medd. fran Lunds Geol. Paltklubb, Ser. B, No. 2 

 (Aftryck ur K. Fysiografiska Siillskapets HandL, N. F., Bd. 17), p. 64, PL I, figs, 27-30. (Described and dis- 

 cussed in Swedish.) 



Obolus (Broggeria) salteri var.? WesterqArd, 1909, Medd. friin Lunds Geol. Faltklubb, Ser. B., No. 4 (Aftryck ur K. 

 Fysiografiska Siillskapets HandL, N. F., Bd. 20), p. 56, PL II, figs. 17-19. (Discussed in Swedish. Figs. 17 

 and 18 are copied from Moberg and Segerberg, 1906, PL I, figs. 28 and 27, respectively.) 



The original description by Holl follows: 



Compressed, subtriangular to nearly round, rather broader than long; shell thin; surface grooved concentrically 

 by a few inequidistant, strongly marked lines of growth and by numerous finer lines which are distinct only on the 

 sides of the shell. Length usually about one-third inch, width slightly more. 



Position. — In the Black Shales. 



Brogger [1882, PL X, figs. 10, 11, and 13] identified this species from both the Oeratopyge slate 

 and the Oeratopyge limestone of Sweden. The specimen from the limestone is very beautifully 

 preserved and appears to be the dorsal valve of this species. 



a The synonymy for this subgenus does not give a complete record o! the various genera under which the species now included in Broggeria were 

 formerly placed; it gives only those references in which the genus is discussed or described. To complete the record the following mere generic 

 references are listed: 



Obolella Holl [1865, p. 102). 



Obolella Davidson [1866, p. 61; 1868, p. 163]. 



Obolus? Dall [1870, p. 163]. 



Obolella Phillips [1871, p. 68]. 



Obolus Brogger [1882, p. 44]. 



Obolus? Mickwitz [1896, p. 19]. 



Obolella ? Matley [1902, p. 139]. 



Obolus (Broggeria) Moberg and Segerberg [1906, p. 64). 



