182 AiDials of the South African Museum. 



are one and the same species, and that Uh'ich's /Sp. chuquisaca from 

 the Devonian of BoHvia, and Von Ammon's Sp. vogeli from Brazil, 

 are also specifically identical with it. Some of Kayser's figured 

 specimens {op. cit., figs. 1, 2) show only 10 ribs, while one (fig. 3) 

 shows 18 ribs much closer together with narrower interspaces, the 

 former resembling Von Ammon's Si^. vogeli, and one of Sharpe's 

 Cape specimens (Sharpe, oj;. cit. pi. xxvi., fig. 6) referred to Sp. 

 orhignyi ; and they probably represent a distinct species or variety 

 for which the name Sp. vogeli may be retained. 



In the figures given by Morris and Sharpe of Sp. orhignyi {op. cit., 

 pi. xi., fig. 3 a 6 c) there are only 14-16 ribs delineated, though the 

 number is stated in the text to be " about 20." In our present 

 specimens from Cape Colony there are from 12-20, but generally only 

 16 ribs even in the largest specimens ; those with the smallest number 

 being mostly of small size and presumably young individuals. In 

 all of them the ribs are rounded, with the interspaces not so wide, 

 and towards the cardinal region the ribs are faint and low ; the 

 hinge-area is always triangular, vertical, and high, being in some 

 cases about one-third the length of the shell ; the cardinal angles are 

 pointed and acute ; the shell is about twice as wide as long or some- 

 times a little less ; the sinus on the pedicle valve is rounded, and the 

 cori'esponding fold on the brachial valve shows in the casts a median 

 sUt representing a septum. 



The types of Sharpe's Cape specimens of Sp. antarcticus and 

 Sp. orhignyi in the Museum of the Geological Society, occur 

 intermixed on the same blocks of sandstone and are quite in- 

 separable. 



A closely allied form is Sj). murchisoni Castelnau," (= Sp. arrectus 

 Hall f ) of the Oriskany Sandstone, as a comparison with a large 

 series of North American Devonian specimens indicates. 



Dimensions. — The largest specimens in this collection attain a 

 width of 60-70 mm., and a length of 40-45 mm. 



Localities.— (Ho. 147) North of Montagu. (No. 154) Just north 

 of Stink Fontein, Ceres. (No. 219) Fossiliferous or 1st Sandstone, 

 north of homestead, Uitkomst. (No. 220) Ditto. (No. 218) Ditto. 

 (No. 217) Ditto. (No. 216) Ditto. (No. 215) Ditto. (No. 119) 

 Warm Bokkeveld, Ceres. (No. 155) Gydo Pass, Ceres. ? (No. Ill) 

 Fossiliferous or 1st Sandstone, near Klein Straat Siding. 



* Castelnau, Essai Syst. Silur. Amer. Septentr. 1843, p. 41, pi. xii., figs. 1, 2. 

 I Hall, Talseont. N.Y., vol. iii., 1859, p. 422, pi. xcvii., figs. 1, 2. 



