606 CAMBEIAN BRACHIOPODA. 



longitudinal line nearly flat from the apex to beyond the center of the valve, where it slopes 

 gently to the anterior margin; on some shells the slope to the apex rises more abruptly and 

 there is a gentle slope from the umbo to the front margin; the posterior margin arches gently 

 upward from the plane of the edges of the front and sides of the valve. Apex directed back- 

 ward and perforated by a minute pedicle opening; it extends a little beyond the posterior 

 margin, and is separated from it by a narrow false area or rim of shell; on some shells an 

 elongate, more or less crescentiform tubercle occurs on each side of the apex, and just back of 

 them at the end of the depression between them the minute pedicle opening occurs, or there 

 may be a thickening of the shell back of the opening which results in a tubercle, as shown in 

 Plate LVII, figure 4d; in other shells there is simply a tliickened rim of shell about the front 

 and sides of the apex with the pedicle opening at the posterior section of it (PI. LVII, fig. 4c). 

 Dorsal valve moderately convex; it slopes rather abruptly from the umbo to the minute mar- 

 ginal beak and gently to the front ; a minute tubercle occurs on each side of the beak of perfect 

 specimens (PI. LVII, fig. 4b). 



Surface marked by concentric fines of growth and low, rounded, more or less obscure 

 radiating ridges that occur on the anterolateral portions, or on the central part, or aU across 

 in front of the umbo and sides, or only as faint traces; in addition there is a system of fine undu- 

 lating, irregular, more or less inosculating, concentric ridges, upon which there are minute 

 rounded tubercles or granules that have no extended sj^stematic arrangement; on some shells 

 the granulated surface extends to the front margin and on others more or less of the front 

 portion of the valves is marked only by concentric lines and traces of the undulating ridges; 

 in some places the granules are arranged in diagonal lines that cross each other obfiquely, and 

 then the effect is a modified form of the surface of Botsfordia pulchra (Matthew). 



The following are measurements of the valves : 



Dimensions of valves of Botsfordia granulata (Redlich). 



Length. Width, 



mm. mm. 



Ventral 6.5 7.5 



Ventral 6. 5 6. 5 



Dorsal 4 5 



Dorsal 4. 5 5 



The specimens are embedded in a fine shale and are more or less flattened by compression. 



The shells are built up of a tlun outer layer and several inner layers or lamellae shghtly 

 oblique to the outer surface. The sheU substance is corneous or, according to the author, 

 "phosphate of fime and chitine" [Redlich, 1899, p. 6]. 



The interior of the ventral valve is essentially the same as that of Botsfordia pulchra 

 (Matthew) and B. cselata (Hall) ; strong main vascular sinuses rise beside the median line close 

 to the posterior margin and gradually diverging, extend forward into the body of the valve 

 nearer to the median line than to the outer margins; the visceral area is about three-eighths 

 the length of the valve and it has a narrow median groove that terminates in a club-shaped 

 anterior end (PI. LVII, fig. 4g) that suggests the heart-shaped cavity of Oholus (PI. VII, figs. 

 1, 3, and 6). The position of the transmedian and anterior lateral muscle scars is shown close 

 beside the main vascular sinus; the central scars and outside and middle laterals can not be 

 separated but the space they occupy is indicated at c, Plate LVII, figure 4p. The cast of 

 the pedicle passage through the shell is shown in figure 4i. 



The interior of the ventral valve is much like that of Acrothde coriacea Limiarsson. (Compare 

 PL LVII, fig. 4k, with PL LVI, fig. le.) There is a median ridge with the main vascular sinuses 

 starting out beside it near the posterior margin and gradually separating as they extend forward 

 into the valve about halfway between the margins of the valve and the median ridge; the 

 cardinal muscle scars are small and close to the median ridge, posterior margin, and main 

 vascular sinuses; the central muscle scars occur on the slope of the median ridge a little back 

 of the center of the valve, and the small anterior laterals close to the median line a little in 

 advance; in young shells the transmedian and middle and outside laterals are combined in 



