CAMBRIAX BRACHIOPODA WALCOTT 7I 



dark bluish-gray and the inner layers shiny bluish-black. The outer 

 surface is marked by concentric striae, and lines of growth with a 

 few indistinct radiating striae; the striae on the dorsal valve bend 

 slightly backward where they cross the median, flattened space. The 

 inner layers have many concentric striae; also numerous fine radi- 

 ating striae. The shell is built up of several layers or lamellae, so as 

 to be strong in the umbonal region and thin toward the edges. 



The largest ventral valve in the collection has a length of 12 mm. 

 and a maximum width of 9.5 mm. at the anterior third of its length ; 

 a dorsal valve 10 mm. long has a width of 7 mm. 



A partially exfoliated ventral valve indicates the presence, on 

 each side of the visceral area, of a strong ridge somewhat similar to 

 that in LinguleUa acutangula (Roemer) [1849, P- 20]. 



Observations. — This fine shell has the general outline of the 

 group of small shells of which LinguleUa ferruginea Salter [Salter 

 and Hicks, 1867, p. 340] is typical. It differs from them in its large 

 size and strong shell. All of the larger species of LinguleUa are 

 either more acuminate or broader in outline. 



The material was collected by Mr. Charles Butts, of the United 

 States Geological Survey, and I take pleasure in naming the species 

 after him. 



Formation and Locality. — Upper Cambrian: (i) Limestones in 

 cut on Louisville and Nashville Railroad, near Woodstock; and (2) 

 limestones near Kimbrcl; both in Bibb County, Alabama. 



LINGULELLA TEXANA, new species 



Plate 8, Figure 5 



This is a small but distinctly marked species, represented by two 

 dorsal valves occurring in the Middle Cambrian limestones of central 

 Texas. The dorsal valves are oval and quite strongly convex. The 

 shell appears to have been rather thick, and the outer surface is 

 marked by strong, radiating striae, which are characteristic of the 

 species. The striae are crossed by fine, concentric striae and lines 

 of growth. The position of the muscle scars and the size and char- 

 acter of the area are shown by fig. 5. 



Formation and Locality. — Middle Cambrian: (i) Limestone 

 near Honey Creek; and (2) limestone near Morgan Creek; both in 

 Burnet County, Texas, (3) Sandstones of Potosi formation, on 

 Flat River, iMissouri. 



