588 FL'OcEEDIXr^S OF THE XATIOXAL MrsEVM. v..l. xxv. 



ACROTRETA IDAHOENSIS ALTA, new variety. 



This is one of the forms that I included with Acrotrda gemma in the 

 report on the paleontology of the Eureka District, Nevada. It has the 

 broad false area of A. Idahotn-sls. but the pedicle valve is more elevated 

 and the apex does not overhang the false area. From A. attenuata it 

 differs in having a broad false area. 



Formation and Joc-ality. — Middle Cambrian, upper portion of 

 Secret Canyon shales. Secret and New York canyons. Eureka District. 

 Nevada. 



ACROTRETA IDAHOENSIS SULCATA, new variety. 



This strongly marked pedicle valve is associated with t^'pical forms 

 of the species, but in its rounded posterior side and strong median 

 groove it is quite distinct. The apex is broken off' so as to show the 

 cast of a small apical callosity and the base of a minute foraminal tube. 



Forniation and locality. — Middle Cambrian, near Paris. Idaho. 

 Collected by Mr. Spence. 



ACROTRETA INFLATA Matthew. 



Lingulellaf inflata Matthew, Trans. Roy. Soc. Canada, III, 1886, p. 33, i«l. v, 



figs. 7, 7a; Trans. X. Y. Acad. Sci., XIV, 189.5, p. 127, pi. v, fig. 3. 

 Lingulellaf inflata var. oralis Matthew, Trans. X. Y. Acad. Sci., XIV, 1895, 



p. 127, pi. V, fig. 4. 

 Acrothyraf inflata Matthew, Bull. Xat. Hist. Soc. Xew Brunswick, IV, 1901, 



p. 303. 

 LinguMla {Acrothyraf) inflata Matthew, Bull. Xat. Hist. Soc. Xew Brunswick, 



IV, 1902, Pt. 5, p. 390. 



Shell subcircular to transversely broad oval. Pedicle valve sub- 

 conical, with the apex directed backward and usually on a line with 

 the po.sterior margin, or extending be3'ond it, but it may be ante- 

 rior to it; false area slightly defined by the abrupt curvature of 

 the cardinal slopes: median line depressed, narrow, the two sides of 

 the false area incurving to form to it; foraminal aperture longitudi- 

 nally oval and slighth' truncating the apex. Brachial valve gently 

 convex, with a minute marginal beak. Surface of shell marked by 

 concentric striw and growth lines, and fine, irregular, wavy stride that 

 inosculate more or le.ss, giving the surface a fretted appearance under 

 a strong lens. The inner surface is marked by concentric lines, also 

 rather strong radiating lines. The shell is built up of the thin, outer, 

 ornamented surface and several thin inner lasers or lamella. The 

 average length of the pedicle valve is 4 mm. and the width 3 to 3.5 

 mm. The brachial valves are usually wider than long. 



Casts of the interior of the pedicle valve show strong cardinal scars, 

 a strong apical callosit}', and rather weakly developed main vascular 

 sinuses. The apical callosity varies in size and in form from elongate 

 oval to subcircular. The cast of the interior of the brachial valve 



