476 CAMBRIAK BRACHIOPODA. 



sinuses (vs) are indicated for the ventral valve in figure Ig, and for the dorsal valve by figures 

 Ih and Ij. The latter are rather indistinct, rounded ridges, with a few lateral branches showing 

 in the specimens. In figure Ig the inteiior lateral branches (ivs) are shown, and the peripheral 

 sinuses (pvs) ai-e seen in figures Ih and Ij, Plate XVII. 



The parietal scar (ps) is distinctly shown in front of the visceral area of the ventral valve 

 (PI. XVII, fig. If), but it has not been traced outside of the main sinus. In one specimen of 

 the dorsal valve its course may be followed from the median line in front of the anterior lateral 

 muscle scars, curving outward to the main vascular sinus and outside of the sinus around the 

 outside lateral, where it turns back toward the flexure line of the area (fig. Ij). 



Observations. — The specimens described by Roemer [1849, p. 420] came from a limestone 

 in San Saba County, Texas. He figures [1852, PL XI, fig. 10] a ventral valve that is larger 

 and more acuminate than the majorit}^ of the specimens in the collection before me; but, in 

 the absence of a closely alhed species from the Cambrian of Texas, and m view of the fact that 

 there is a considerable range of variation in the form of the valves, I do not hesitate to identify 

 the form here described as belonging to the species studied by Roemer. He compares it [1852, 

 p. 90] with "Lingula cuneata" of the Medina sandstone of New York, to point out that it is more 

 acuminate than that species. It also differs from it in the character of the interior markings 

 and muscle scars and the greater thickness of the shell. From other species of the genus, 

 Lingulella acutangula varies in form and in the arrangement of the muscle scars. It is some- 

 what closely related to Lingulella cuneola (Wliitfield) of the Mddle Cambrian of the Black Hills, 

 South Dakota, and the latter species may even be identical with it. 



Formation and locality. — TTpper Cambrian: (141)) Limestone on Cold Creek at north end of gorge opposite the 

 north end of Sponge Mountain, 2 miles (3.2 km.) south of the San Saba County line, in Llano County; (14i) upper 

 part of the limestone exposed 1 mile (1.6 km.) west of Cherokee, San Saba County; (353) limestones [see Roemer, 

 1849, p. 420] on San Saba River, San Saba County; (68 and 68e) interbedded limestone and sandstone, Packsaddle 

 Mountain, Llano County; (69) limestone, near Honey Creek, Burnet County; (67 and 67c) sandstone on Tatur Hill, 

 7 miles (11.2 km.) northwest of Burnet, Burnet County; (353c) heavy dark ferruginous sandstone collected somewhere 

 in Llano County; and (70 and 70e) limestone, near Morgans Creek, Burnet County; all in Texas. 



Middle Cambrian: (llj) Basal part of Bonneterre limestone. Mine Lamotte, Madison County; and (Ilk) limestones 

 of the "Edgewise beds," beneath the Elvins formation, St. Francois County; both in Missouri. 



(17c) Sandy limestone, 235 feet (71.6 m.) above the "Tonto" sandstone, Grand View trail, north of Last Chance 

 copper mine, south side of the Grand Canyon of the Colorado, Arizona. 



Specimens that are somewhat doubtfully referred to LingitMJa acutangula occur at the 

 following localities: 



Upper Cambrian: (327) Arenaceous limestone east of Gold Camp, in the Caballos Mountains, Sierra County, 

 New Mexico. 



(Ill) Arenaceous limestone of the Elvins formation, 50 feet (15.2 m.) above the "Edgewise beds," St. Francois 

 County, Missouri. 



Middle? Cambrian: (313c) Limestone 12 miles (19.3 km.) west-southwest of Alpha Station, Eureka County, 

 Nevada. 



Lingulella agnostoeum (Wallerius). 

 Plate XXX, figure 15. 



Lingula agnostorum Wallerius, 1895, Undersokningar ofver Zonen med Agnostus Ixvigatus i Vestergotland, pp. 64-65, 

 figs. 8a-b. (Described in Latin, and discussed in Swedish, as a new species.) 



Shell very small. Outline ovate, with the ventral valve subacuminate; moderately convex. 

 Surface of shell marked by concentric strife and strong growth lines that, near the umbo, form 

 deep undulations separating the minute, elevated, smaller umbo from the less elevated con- 

 centric ridges in front of it. The ventral valve illustrated by Wallerius is about 3 mm. in length 

 and that of the specimen before me is 1.5 mm. I have not seen a dorsal valve. 



Observations. — This minute shell is associated with Acrotreta farvula (Wallerius) and 

 Agnostus Isevigatus. It differs from Lingulella sp. undt. a of the Olenus truncatus zone in its 

 minute size, more acute beak, and less distinctly striate surface characters. 



