SYNTKOPHIIDtE. 799 



All of the species of the Syntrophiidfe with nonplicated, smooth surface and spondylium 

 raised on a median septum are referred to Syntrophia, and the species with a more or less 

 plicate surface, with sessile spondylium or pseudospondylium, to the genus Huenella. The 

 nonplicate or smooth species are: S. camhria and S.? unxia of the Middle Cambrian; S. alata, 

 S. harahuensis, S. camphelli, S. orihia, S. primordialis, and S. rotundata of the Upper Cambrian; 

 and S. calcifera, S. lateralis, and S. nundina of the Ordovician. 



Syntrophia alata Walcott. 

 Plate cm, figures 3, 3a-e. 

 Syntrophia alata Walcott, 1905, Proc. U. S. Nat. Mus., vol. 28, p. 290. (Characterized as below as a new species.) 



This species is characterized by its transrerse form and extended cardinal angles. Exterior 

 surface marked by concentric striae and lines of growth and interior surface by fine, radiating 

 striae. A transverse section of the ventral valve at the umbo shows the spondylium with a 

 strong median septum supporting it. The interior of the ventral valve was marked by two 

 strong main vascular sinuses starting from the sides of the spondylium. 



Formation and locality. — tTpper Cambrian: (69) Limestone near Honey Creek, Bm-net County, Texas. 

 Syntrophia barabuensis (A. Winchell). 

 Plate CII, figures 1, la-g. 



Orthis barabuensis A. Winchell, 1864, Am. Jour. Sci., 2d ser., vol. 37, p. 228. (Described and discussed as a new 



species.) 

 Leptxna barabuensis (Winchell), Whitfield, 1878, Ann. Rept. Wisconsin Geol. Survey for 1877, p. 60. 

 Leptxna barabuensis (Winchell), Whitfield, 1882, Geology of Wisconsin, vol. 4, pt. 3, pp. 171-172, PI. I, figs. 6 and 7. 



(Described and discussed; see below for copy.) 

 Leptaena barabuensis Winchell, Whitfield, 1882, idem, p. 195, PL III, fig. 6. (Described from a higher horizon than 



that containing the specimens referred to in the preceding.) 

 Syntrophia barabuensis (Winchell), Hall and Olaeke, 1893, Nat. Hist. New York, Paleontology, vol. 8, pt. 2, p. 216. 



(Changes generic reference.) 

 Syntrophia barabuensis (Winchell), Walcott, 1905, Proc. U. S. Nat. Mus., vol. 27, pp. 290-291. (Description by 



Whitfield copied, and species discussed as below.) 



The description by Whitfield [1882, pp. 171-172] follows: 



Shell of medium size or smaller, measuring about half an inch or less than half an inch along the hinge line; 

 form semielliptical, longest on the hinge and more than half as wide again as long; extremities of the hinge often sub- 

 mucronate; front of the valves rounded or slightly emarginate in the middle. Ventral valve the most convex, and 

 marked by a strong, angular mesial elevation, nearly one-fourth as wide on the front of the valve as the width of the 

 shell; area moderately high and nearly in the plane of the valve; cardinal borders very gradually sloping from the 

 center to the extremities of the cardinal line. Dorsal valve less convex than the opposite, and marked by a suban- 

 gular mesial depression, corresponding to the fold of the opposite valve; area linear. Surface of the shell apparently 

 smooth, or at least so far as can be determined from either the internal casts or from the matrix. 



I had some doubt regai-ding the positive identity of this species with that described by Professor Winchell [1864, 

 p. 228] in consequence of the following remarks which occur in his description: "Surface with sixteen or eighteen ribs 

 visible on the casts, the strongest of which limit the mesial sinus," and again, "apparently of the type of Orthis biforta." 

 In examining a number of specimens, I had not been able to detect any strise or ribs, and felt somewhat inclined to 

 regard it as a distinct species from that one. I have, however, through the kindness of Prof. W. [Winchell], been able 

 to make a direct comparison with one of his original specimens, and should consider them as identical. The specimen 

 sent me has the mesial told (of the ventral valve) remarkably strongly defined by a depressed line on each margin, the 

 center appearing tumid, which I think is in part due to accident. The specimen coiTesponds closely with the ventral 

 valve we have figured, except in the strongly defined mesial fold. 



Observations. — Tliis is the same type of Syntrophia as S. primordialis. It differs in its 

 more rounded outlines, shallow, rounded sinus in the ventral valve, and, usually, a less pro- 

 nounced fold on the dorsal Valve. Evidence of a short median septum at the end of a very 

 short spondylium in the dorsal valve is shown by one cast (PL CII, fig. Ig). 



The species derives its specific name from its occurrence at Devils Lake, which is near 

 Baraboo, Sauk County, Wisconsin. 



Formation and locality. — Tipper Cambrian: "St. Croix sandstone " at the following localities: (328 [Whitfield, 

 1882, p. 172]) Upper layers near the north end of Devils Lake, Sauk County; (81b) near Devils Lake, Sauk County; (81o) 



