710 CAMBRIAN BRACHIOPODA. 



(320d) Exsulans limestone in the lower part of the Paradoxides tessini zone, at Fogelsang, 5 miles (8 km.) east of 

 Lund, Province of Malmohus, Sweden. 



(310c [Wallerius, 1895, p. 66]) Limestone of the Paradoxides mlandicus zone, on Oeland Island; (310p [Linnarsson, 

 1876, p. 18]) limestone of the Paradoxides alandicus zone at Borgholm; and (310b) dark-brown limestone at Borgholm, 

 on Oeland Island; all in Sweden. 



(16j) Limestone of the Paradoxides forchhammeri zone at Laesaa; (161i) limestone of the same zone at Borregaard; 

 and (334 [Wallerius, 1895, p. 66]) limestone of the Paradoxides forchhammeri zone; all on Bornholm Island, Denmark. 



ACROTRETA SEEBACHI Walcott. 

 Plate LXXVII, figures 3, 3a. 



Acrotreta seebachi Walcott, 1902, Proc. U. S. Nat. Mus., vol. 25, pp. 598-599. (Described and discussed as below 



as a new species.) 

 Acrotreta seebachi Walcott, Moberg and Segerberg, 1906, Medd. Iran Lunds Geol. Faltklubb, Ser. B, No. 2 (Aftryck 



ur K. Fysiografiska Sallskapets Handl., N. F., Bd. 17), pp. 66-67. (Characterized and discussed in Swedish.) 



Among the fragments of trilobites in the Ceratopyge hmestone collected by Schmalensee 

 there are a few specimens of a species of Acrotreta distinct from A. scJimalenseei Walcott and 

 A. socialis von Seebach. The ventral valve is relatively low, with the false area nearly vertical. 

 A cast of this valve shows the cardinal scars on each side high up toward the apex; small main 

 vascular sinuses and apical callosity. False area rather large and marked by a slight indica- 

 tion of a median depression that is recognized by a slight undulation in the transverse striae. 

 Surface marked by fine threadlike concentric strife and lines of growth. A broken dorsal 

 valve has a broad median sulcus and a small distinct beak at the posterior margin. The 

 valves are slightly transverse. A large ventral valve measures 3 mm. in width by 2.5 mm. 

 in length. 



The surface striae and the cardinal scars serve to distinguish this species from others known 

 to me. Acrofhelef ceratopijgarum (Brogger) is from the Ceratopyge shales, but it has a low 

 ventral valve with the false area sloping forward. 



After deciding that a new species was represented in the material received from Schmalen- 

 see, I studied a fine series of specimens that Dr. W. C. Brogger kindly sent me. In material 

 collected by Schmalensee from the Ceratopyge shale at Borgholm, Oeland Island, Sweden, 

 some imperfect specimens suggest Acrotreta seehacM; they might equally well be referred to 

 A. carinata Moberg and Segerberg, or A. circularis Moberg and Segerberg. 



The specific name was given in honor of Dr. K. von Seebach. 



Formation and locality. » — ^Passage beds between the Upper Cambrian and the Ordovician: (8x) Ceratopyge, 

 limestone at Slemmestad, about 3 miles (4.8 Jem.) southwest of Christiania; (323d) Ceratopyge limestone (Etage 3aj- of 

 Brogger) at Christiania; (323f) lower part of the Ceratopyge limestone [Brogger, 1882, pp. 16 and 17] at Vestfossen, 10 

 miles (16.1 km.) west-southwest of Christiania; (323h) blue Ceratopyge limestone [Brogger, 1882, p. 17] at Vestfossen, 

 10 miles (16.1km.) west-southwest of Christiania; and (323e) Ceratopyge limestone at Engervik, near Christiania; all 

 in Norway. 



Upper Cambrian: (310d) Cerotopj/g'e slate at Borgholm, Oeland Island, Sweden. 



Specimens somewhat doubtfully referred to this species occur at the following locality: 



Passage beds between the Upper Cambrian and the Ordovician: (323g) Ceratopyge limestone (Etage Sa;- of 

 Brogger), at Vaekkero, in the Christiania region, Norway. 



Acrotreta shantungensis Walcott. 



Plate LXIX, figures 5, 5a-e. 



Acrotreta shantungensis Walcott, 1905, Proc. U. S. Nat. Mus., vol. 28, pp. 301-302. (Described and discussed as below 

 as a new species.) 



Shell small. Ventral valve a low cone with the apex a little forward of the posterior 

 margin, which is slightly flattened; apex minute, directed backward and projecting slightly 

 over the faintly defined false area. The cast of the interior shows that the apical callosity was 

 rather large and that the main vascular sinuses were well defined on each side of it ; the cardinal 

 scars are small and not prominent. 



a Localities 8x and 310d are represented in tlie collections of the United States National Museum; the others are in the collection of the 

 University of Christiania. 



