266 Annah of the SontJi Africcm Muscnvi. 



Dimensions. — Length (along cardinal line) about 35 mm, ; height 

 (along anterior margin) about 43 mm. 



Affinities. — The only species of the genus Bijssopteria described 

 by Hall '■' is B. radiata, Hall, from the Chemung Group ; and it has 

 a similar shape and ornamentation, but the posterior wing is not 

 distinctly marked off from the body, 



Localif)/. — (No. 82) Fossiliferous Sandstone (near Uitkomst ?). 



ACTINOPTEEIA aff. BOYDI (Conrad). 

 (PI. XXXII., fig. 9.) 



One left valve (No. 81) in a fairly good state of preservation but 

 with part of the posterior wing broken off is the sole representative 

 of this genus in this collection. The shell is very oblique, elongate 

 and subrhomboidal ; the body is strongly convex, but flattens out pos- 

 teriorly into the posterior wing, from which it is only sharply marked 

 off for a short distance behind the umbo. The umbo is acute, 

 pointed, rather prominent and nearly terminal. The umbonal angle 

 is about 30°. The hinge-line is straight, but its length cannot be 

 determined as it is imperfect behind. The anterior ear is narrow, 

 elongate, extending between one-third and one-half the length of the 

 shell, convex, and separated by a strong furrow from the body of 

 shell. The posterior wing is large, triangular?, flattened, depressed, 

 and only defined anteriorly by a furrow from the body of the shell. 

 The surface of the shell is marked by numerous faint low radiating 

 ribs, apparently weakly subnodulose, and crossed by several strong 

 concentric growth-wrinkles. The ribs are obsolete or nearly so on 

 the posterior wing. The anterior ear is ornamented with concentric 

 striae. 



Dimensions. — Length about 35 mm ; height about 27 mm. 



Affinities. — The nearest ally of this form seems to be A. boydi, 

 Conrad, i of the Hamilton Group, but the anterior ear in our specimen 

 is rather longer. 



Ulrich I describes a species of Actinopteria from the Devonian of 

 Bolivia, wliich he compares with the same species. 



* Hall, Palffiont. New York. vol. v., pt. i., Lamell. i., 1884, p. 2o'2, pi. xxxii., 

 figs, 21, 22 ; pi. Ixxx., fig. 11. 



t Hall, ihid.. p. 113, pi. xix., figs. 2-30. 

 X Ulrich, oi>. cit., p. 50, t. iii., figs. 1-3. 



