394 



Annals of the South African Museum. 



at about 130° ; numerous small teeth in front of beaks, extending 

 about half-way down anterior end ; posterior hinge-Hne not preserved. 

 Anterior adductor scar long, pointed oval, situated at about middle 

 height of anterior end. Posterior adductor scar of same shape and 

 situated rather more than half-way between the beaks and the 

 posterior end close to dorsal margin. Faint posterior excavation 

 in pallial hne. 



Dimensions. — Length 12-5 mm. ; height 10 mm. ; thickness 4 mm. 



Locality. — Zwartberg Pass. 



Bemarks. — One internal cast is all the material available, but 

 luckily it is well preserved. I am inclined to refer this shell to the 

 genus Nuculana rather than to Nucula because of the excavation in 

 the pallial line which is just visible. It is unusually short and 

 triangular in shape and is certainly distinct from N. viator. 



Genus NUCULA Lamarck, 1799. 



NUCULA NIGELLA sp. nov. 



(PI. XLVIL, figs. 13, 13a.) 



There is one internal cast of a nuculiform shell from Zwartberg 

 Pass which must be placed in a new species of the genus Nucula. 

 It is slightly abraded at the anterior and posterior ends, but the 

 characters exhibited are quite sufficient to establish its inde- 

 pendence. 



Description. — Shell trigonal, swollen anteriorly, compressed 

 posteriorly, about four-fifths as high as long. Anterior end thick, 

 flattened, abruptly truncated, almost vertical. Dorsal margin straight, 

 short, not longer than anterior end is high, with which it makes 

 angle of about 75°. Beaks anterior; slightly sw^ollen and scarcely 

 elevated, not recurved. Lunule large, elongate, extending about 

 two-thirds dow^n the anterior end, slightly impressed but not 

 markedly concave. Ventral margin short, convex, curving round 

 regularly into broadly rounded posterior end of shell. Hinge-line 

 straight behind beaks, with 20-30 small transverse teeth extending 

 about three-fourths along dorsal margin in narrow lanceolate area 

 (impressed in cast). Ligamental pit between beaks well marked, 

 deep. Anterior hinge-line not preserved. Posterior muscle-scar 

 below end of hinge-line, strong. 



Dimensions. — Length of shell 31 mm. ; height 25 mm. ; thickness 

 (anteriorly) 17 mm. 



Bemarks. — It is possible that this is the internal cast of the shell 



