ACROTRETID^. 639 



AcEOTHELE BOHEMiCA (Barrande) . 



Plate LVII, figures 1, la-d. 



Oholusf bohemicus Barrande, 1879, Systems siliirien du centre de la Boheme, vol. 5, pt. 1, PI. CII, figs, vn: 1-3. 



(Not described, but figured as a new species. Figs, vn: 1-2 are reproduced in this monograph, PI. LVII, figs. 



1 and la, respectively.) 

 Acrothele bohemica (Barrande), Walcott, 1886, Bull. U. S. Geol. Survey No. 30, p. 107. (Merely changes generic 



reference.) 

 Acrothele bohemica (Barrande), Hall and Clarke, 1892, Nat. Hist. New York, Paleontology, vol. 8, pt. 1, p. 101. 



(Suggests reference to Acrothele.) 

 Acrothele bohemica (Barrande), Pompbckj, 1896, Jahrb. K.-k. geol. Reichsanstalt for 1895, Bd. 45, Hft. 3, pp. 509-511, 



PI. XIV, figs. 7-15. (Described and discussed in German. Figs. 8b, lib, and 10b are reproduced in this 



monograph, PI. LVII, figs, lb, Ic, and Id, respectively.) 



Barrande did not publish a description of this species, but Pompeckj [1896b, p. 509] gives 

 an extended description based on a large number of specimens. From this and the accom- 

 panying illustrations it appears that the general form is much like that of Acrothele coriacea 

 Linnarsson. It differs from the latter in having the apex nearer the posterior margin and 

 in having a concentrically striated surface and undulating hnes instead of granulose surface; 

 these characters also distinguish A. bohemica from A. {BedlicKella) granulata (Linnarsson). 

 The student should carefully examine the series of figures accompanying Pompeckj's descrip- 

 tion as well as those of Barrande. Copies of the latter are inserted on Plate LVII, figures 1 

 and la, and copies of Pompeckj's figures on Plate LVII, figures lb, Ic, and Id. 



The posterior position of the apex of the ventral valve suggests in this respect Acrothele 

 prima (Matthew) (PI. LXI, fig. 6) and Acrothele prima costato ' (Matthew) (PI. LXI, figs. 4 

 and 4a) , but in surface characters and outUne of the valves the species differ, as indeed they do 

 in the apex of A. prima being nearer the margin than that of A. bohemica. Comparison should 

 be made with A. quadrilineata Pompeckj, which is closely allied to this species. 



The specific name is derived from Bohemia. 



Formation and locality. — Middle Cambrian: (345 [Pompeckj, 1896b, p. 509]) Greenish shale in the Paradoxides 

 zone, on the Dlouhd Hora, above the brook of Sbirov, near Skrej; (345a [Pompeckj, 1896b, p. 511]) shales in the Para- 

 doxides zone, on the right bank of the brook of Kardsek, near Tejfovik; (3451) [Pompeckj, 1896b, p. 511]) in the 

 "Bande de Jinec," at Felbabka and Jinec; and (345c) in Etage C [Barrande, lS79b, PI. CII], at Mleschitz; all in Bohe- 

 mia, Austria-Hungary. 



ACEOTHELE BOEGHOLMENSIS Walcott. 



Plate LXIII, figures 2, 2a-b. 



Acrothele borgholmensis Walcott, 1908, Smithsonian Misc. Coll., vol. 53, No. 3, pp. 84-85, PL VIII, fig. 12. (De- 

 scribed and discussed as below as a new species. Figs. 12 and 12' are copied in this monograph, PL LXIII, 

 figs. 2 and 2a, respectively.) 



General form subcircular to broad oval. Ventral valve subcortical, with the apex a short 

 distance back of the center. A clearly defined false area extends from the apex to the margin ; 

 it is defined by a shght depression and a low ridge at the outer edges ; two or three longitudinal 

 Hnes extend to the margin, and the concentric Hnes of growth of the shell cross it without inter- 

 ruption. An elongate, small foraminal aperture occurs just back of and beneath the apex. 



The outer surface of the shell is of a dull, dark color, and marked by sHghtly undulating, 

 clearly defined, concentric strias; the inner layers are marked by fine radiating and concentric 

 fines. The shell is built up of tliin lamellae arranged in concentric layers that are sHghtly 

 obHque to the surface layer. Shell substance corneous. Nothing is known of the interior 

 of the valves except tlie sharp median ridge of the dorsal valve. 



The largest specimen has a diameter of 4 mm.; the average size is about 3 mm. 



Observations. — The convexity, position of tlie apex, and clearness of the false area depend 

 upon the degree of compression and distortion the shells have received. I have described 

 what appears to be the uninjured shell. 



