662 CAMBRIAN BRACHIOPODA. 



associated with A. yorkensis is of the Middle Cambrian type of the interior trough and 

 quite unlike that of the Paradoxides fauna of the Atlantic Coast Province. In size this species 

 approaches A. {Redlichella) granulata (Luinarsson), but it differs from that species in its miuutely 

 granulated surface. 



This species derives its specific name from its occurrence near York, Pennsylvania. 



Formation and locality. — Middle Cambrian: (48d) Argillaceous shales in railroad cut alongside of gas house, 

 city of York, York County, Pennsylvania. 



AcROTi-iELE sp. undt. a. 

 Plate LXIII, figure 5. 



This species is represented by a single specimen of a cast of the interior. This cast shows 

 the base of the apical opening, wlaich is rather large, a short visceral cavity, the central 

 portion of which was somewhat elevated, and clearly defined main vascular sinuses that originate 

 at the sides of the base of the pedicle opening, and extend forward well toward the front of the 

 valve, gradually diverging at the center, so as to be about one-third the distance from the 

 median ridge to the margin; rather strong muscle scars occur beside the main vascular sinuses, 

 where the latter curve forward into the body of the valve. Two scars, the transmedian and 

 anterior lateral, are clearly shown. A fragment of the shell is preserved back of the cast of 

 the pedicle opening that indicates that the shell was rather tliick over the umbonal portions. 



The specimen has a length of 7 mm., with the breadth the same. Nothing is known of 

 the exterior surface. The interior shows a few obscure Unes of growth and fine radiating striae. 



This species suggests the ventral valve of Acrothele yorkensis Walcott in form, but in the 

 absence of an exterior or other characters for comparison, no specific designation is given to it. 



Formation and locality. — Lower Cambrian: (319b) Conglomeratic limestones containing OZeneZZwsf, St. Simon, 

 Province of Quebec, Canada. 



_- Acrothele sp. undt. Moberg. 



Acrothele Moberg, 1892, Geol. Foren. i Stockholm Forhandl. for 1902, Bd. 14, Hft. 2, pp. 114-115, PI. Ill, fig. 9. 

 (Described in Swedish; see below for translation.) 



Moberg describes the species as follows: 



Of this genus, none but exfoliated specimens have been met with . They do not appear to show characters sufficient 

 for specific determination. The shell has an almost circular circumference, with the back edge, along a distance 

 constituting about one-fifth of the whole circumference, somewhat truncated. From the apex, which is situated 

 near the posterior margin, the shell slopes pretty evenly both toward the anterior and the posterior margins, so that 

 these two parts form approximately a right angle with each other at the apex. Traces of concentric lines of growth 

 are visible. 



In the position of the apex and the convexity of the ventral valve the cast of this shell 

 is much hke that of the forms from the Lower Cambrian of Bic, Canada (PI. LXIII, fig. 5). 



Formation and locality. — Lower Cambrian : (310e) Sandstone bowlder on the beach between Eherum and Stora 

 Ror; (SlOf) sandstone bowlders west of Ekerum; and (310g) sandstone bowlders south of Stora Ror; all [Moberg, 1892b, 

 p. 115] on Oeland Island, Sweden. 



REDLICHELLA Walcott, a subgenus of ACROTHELE. 



Acrothele {Redlichella) Walcott, 1908, Smithsonian Misc. Coll., vol. 53, No. 3, pp. 89-90. (Described and discussed 



as below as a new subgenus.) 

 Acrothele {Redlichella) Walcott, 1908, idem, vol. 53, No. 4, pp. 142 and 146, and PL XI. (Classification of subgenus.) 



Tills subgenus of Acrothele has all the external characters of the type species of Acrothele, 

 A. coriacea Linnarsson. It differs in the interior markings of the valves. The visceral area 



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

 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: 



Acrothele Linnarsson [1S76, p. 24]. 

 Acrothele Swanston [1877, PI. VII, flgs. 20a-c]. 

 Acrothele lyinnarsson [1877, p. 373]. 

 Acrothele Davidson [18S3, p. 214]. 



Acrothele Walcott [ISSOb, p. 109]. 



Acrothele Swanston [188G, PI. VII, figs. 20a-c]. 



Acrothele Hall and Clarke [1892c, p. 100]. 



