604 CAMBRIAN BRACHIOPODA. 



the apex nearly to the front margin in old shells ; in young shells it rises with a gentle slope from 

 the front margin to the umbo ; the posterior margin, including some distance along the cardinal 

 slopes, rises and arches gently above the plane of the edges of the front and sides of the valve, 

 which brings the apex or beak close to the posterior margin (PL LIX, fig. lb) ; pedicle opening 

 small and at the point of the apex or beak. 



Dorsal valve more broadly ovate in outline than the ventral, moderately convex, and rather 

 strongly arched toward the beak, which is marginal; the arching of the posterior portion of the 

 valve causes it to fit closely into the upward arching posterior margin of the ventral valve ; a 

 shallow median sinus of varying strength and width extends from the umbo toward the front 

 margin, where it usually disappears. 



Surface highly ornamented by narrow, closely arranged, concentric, elevated, irregular, and 

 often inosculating lines, on which small round pustules are lined in such a manner as to give a 

 beaded effect to the surface. The width of the ridges and size of the pustules vary on shells 

 from the same locaUties and from different locaUties. Often the shells have been worn by attri- 

 tion so as to be almost smooth, the coarser striae and hues of growth alone remaining; in addi- 

 tion some shells have more or less numerous, rounded, depressed, radiating ridges, which may 

 be quite regular (PI. LIX, fig. Ih) or very irregular and discontinuous (PL LIX, fig. Ic) ; some 

 shells are without traces of the radiating ridges and others have only the faint outhnes of them. 

 The inner layers are usually shiny and marked by concentric hnes and striae, and numerous fine 

 radiating striae. 



Shell substance corneous; shell rather tliin when young, increasing to a rather strong shell 

 in large specimens; it is built up of a rather tliin outer layer and several inner laj^ers or lamellae. 

 The largest ventral valve has a length of 10 mm., width of 8 mm., toward the anterior margin; 

 as this shell has been broken near the beak and also at the anterior margin, it probably had a 

 length of 12 to 13 mm. 



The interior of the ventral valve shows strong main vascular sinuses, which originate near 

 the pedicle opening, and gradually separate as they extend forward into the valve; beyond the 

 center they curve sUghtly inward and terminate about the anterior fifth of the length of the 

 valve. A small visceral area extends a short distance forward between the main vascular 

 sinuses; it has a narrow depressed space across the front (PL LIX, fig. Ig) that indicates the 

 position of the central, outside lateral, and middle lateral scars; the furrow that extends from 

 near the center of the visceral area to the pedicle opening near the posterior margin is clearly 

 indicated on figure le; as the pedicle opening was at the extreme end and with only a very 

 narrow listrium between it and the posterior margin, the cast of it, or any trace of it, is very 

 difficult to find ; tliis is rendered doubly so by the thin posterior portion of the shell breaking off 

 both before being embedded in the sediment and when being worked out of the rock. There 

 may have been a narrow area, but it has not been seen, and nothing definite is known of the 

 muscle scars. 



The interior of the dorsal valve shows a short narrow area, from which a rather broad, low, 

 median ridge extends forward beyond the center of the valve; a narrow septum is indicated 

 along the posterior portion of the ridge; strong main vascular sinuses originate beside the 

 median ridge at the back and diverge gradually as tliey extend into the valve; the position of 

 the central and lateral muscle scars appears to have been the same as in Oholus (PL LIX, fig. 1 1), 

 but they have not been clearly distinguished except one central scar (h) ; the cardinal muscle 

 scars are large and situated outside of the main vascular sinuses about their own length in 

 advance of the area. 



Observations. — This species, Hke Botsfordia granulata (Redhch), is characterized by having 

 the pedicle aperture close to the posterior margin; it also has the same O&oks-like arrangement 

 of the visceral area, vascular sinuses, and muscle scars in the ventral valve; it differs in outline, 

 surface, and interior markings from B. granulata. 



When studying the genus Lingulella in 1S98 I left Lingulella cselata (Hall) out of the list of 

 species of Lingulella [Walcott, 1898b, p. 393], as I was satisfied that it did not belong there, but 



