SIPHONOTRETIDiE. 617 



^_, Teematobolus excelsis Walcott. 

 Plate LXXXII, figures 8, 8a-b. 



Treimtoholus excelsis Walcott, 1908, Smithsonian Misc. Coll., vol. 53, No. 3, pp. 80-81, PL VIII, fig. 8. (Described 

 and discussed as below as a new species. Fig. 8 is copied in this monograph, PL LXXXII, fig. 8.) 



Shell transversely oval in outline, with both valves obtusely aciimuiate. .Ventral valve 

 strongly convex, with the minute beak at the posterior margin above a low area; the slope 

 from the highest point of the valve, a little back of the center, is greatest toward the beak 

 and nearly uniform to the front and sides of the valve. Pedicle opening unknown, as no 

 exterior or cast of the exterior of the valve occurs in the material collected; two casts of the 

 interior show the cast of the foramen at about the same position as in T. msigrms Matthew and 

 other species of the genus. Dorsal valve shghtly more transverse than the ventral and about 

 two- thirds as convex; a very slight median flattening occurs at the anterior margin that extends 

 back on the valve, nearly to the beak in some specimens; otherwise the convexity is distributed 

 as in the ventral valve. 



Surface marked by a few concentric lines of growth. The shell is rather thin, except 

 over the umbonal and posterior portions of the ventral valve, where it is moderately thick. 

 Its substance is now calcareous, and appears like that of T. insignis; the original shell may 

 have been calcareocorneous. A ventral valve 18 mm. in length has the same width; a large 

 dorsal valve 22 mm. long has a width of 27 mm. 



The area of the ventral valve is short and divided midway by a depressed subtriangular 

 false pedicle furrow; the presence of pits on each side of the anterolateral margins of the 

 false pedicle furrow indicates that the area at these places projected m the same manner as 

 that of T. insignis Matthew and T. Icempanum (llatthew). (Compare PL LXXXII, fig. 8, 

 with PI. LXXXIII, fig. Ic, and with PL LXXXIV, fig. 5.) The cast of the interior of the 

 ventral valve shows a median ridge with the cast of the pedicle opening at about the posterior 

 sixth of the length of the valve; only the imperfect outlines of the splanclmoccsle are known; 

 the main vascular sinuses are outhned for a short distance back of the transverse center suffi- 

 ciently to indicate that their position was about the same as in T. Jcem/panum. The position 

 of the anterior lateral (j) muscle scar is clearly shown just outside of the main vasctdar sinuses; 

 it is elongate oval in outline and a little in advance of the transmedian scar (i) ; the umbonal 

 muscle scars are close to the median furrow, as in T. Jcempanum. 



Interior of dorsal valve unknown. 



Observations. — This fine species differs from all other laiown species of the genus in having 

 the ventral valve more convex than the dorsal and in its greater size. It is the oldest species 

 of the genus, occurring as it does well down in the section of the Lower Cambrian strata, in 

 association with Olenellus. There are a large number of specimens of the exterior of the 

 dorsal valve, but only two interior casts of the ventral valve. The dorsal valve of T. pristinus 

 (Matthew) and T. Icempanum (Matthew) also greatly outnumbers the ventral valve in the 

 collections. This circumstance may be owing to the presence of the foraminal furrow and 

 interior median furrows; these would cause the shell of the ventral valve to break more readily 

 than that of the dorsal. 



Formation AND LOCALITY. — Lower Cambrian : (53) Sandstones in the lower portion of Sd of the Waucoba Springs 

 section; (312) sandstones of 3d of the Waucoba Springs section; and (312a) shales of 3b of the Waucoba Springs section; 

 all east of the Saline Valley road, east of Waucoba Springs [see Walcott, 1908f, p. 187, for position in section], Inyo 

 County, California. 



(176 and 178a) Shales and interbedded limestones between massive limestones containing Arehxocyathus at 

 the south end of Deep Spring Valley; and (176a) sandstone on ridge east of the head of Mazouka Canyon, Inyo Range; 

 both in Inyo County, California. 



Teematobolus insignis Matthew. 



Plate LXXXIV, figures 5, 5a-e. 



Trematoholus insignis Matthew, 1893, Canadian Rec. Sci., vol. 5, pp. 276-279, figs, la-d, p. 276. (Described and 

 discussed as a new species. The specimens represented by figs, la and lb are redrawn in this monograph, PL 

 LXXXIV, figs. 5b and 5, respectively. Figs. 5c and 5a of this monograph are drawn from casts of the typical 

 specimens, Matthew, 1893a, figs, la and lb, respectively.) 



