Neio Fossils from the Bokkeceld Beds. 397 



Genus SOLENOPSIS McCoy, 1844. 



SOLENOPSIS ? BOKKEVELDBNSIS sp. nov. 



(PL XLVIIL, fig. 1.) 



Shell very elongated, narrow, about three times as long as high, 

 narrowing a little anteriorly, moderately convex, compressed a little 

 in the posterior cardinal region ; dorsal and ventral margins sub- 

 parallel ; hinge-line straight ; ventral margin nearly straight or very 

 weakly convex ; anterior end very short, rounded ; posterior end 

 rounded. Beaks low, broad, obtuse, rounded, not rising above 

 hinge-line, situated very far forward, subanterior. Surface of shell 

 divided into two unequal parts by shallow straight groove running 

 obliquely from beak to posterior end of shell ; above this groove the 

 shell is rather flattened and marked by closely-set, fine thread-like 

 minutely nodulated concentric lines. The groove bounds posteriorly 

 the low broad rounded umbonal ridge which merges in front into the 

 general convexity of the shell ; the ridge itself immediately below the 

 groove is marked by 12-15 fine regular equal and equidistant radiating 

 thread-like lines, crossed at right angles by a continuation of the 

 concentric lineation of the posterior slope and nodulated at the 

 points of intersection. In front of these radiating lines the shell 

 is marked by strong rounded concentric growth-ridges, and in- 

 distinctly by a continuation of the finer concentric lineation 

 obscurely nodulated. 



Dimensions. — Length 50 mm. ; height 17 mm. ; thickness 

 11 mm. 



Localitij. — Zwartberg Pass. 



Remarks. — This shell may belong either to the genus Pholadclla 

 or the genus OrtJionota sens, str., or to the genus Solenopsis. The 

 difference in ornamentation of the anterior and middle portions 

 agrees with Pholadclla. But though it apparently lacks the charac- 

 teristic truncation of the posterior end, it has the elongated shape, 

 the depressed broad beaks, the oblique groove behind the umbonal 

 ridge, and long straight hinge-line of Orthonota. Some species of 

 Solenopsis, as defined by Beushausen {op. cit., pp. 216, 217), bear 

 much similarity to it, particularly as regards the shape of the shell 

 and low subanterior beaks ; radial lineation appears to be sometimes 

 present ; and S. vetusta (Goldf.) and S. attenuata (Whiteaves) have 

 a general resemblance to it, so that it may not unreasonably be 

 referred to this genus rather than to any other. 



