420 MOLLUSCA. 
rior end smallest, acutely rounded: posterior end broadly rounded, 
obscurely truncate: colour dingy white, with numerous tented rusty 
blotches, the larger ones arranged somewhat in four radiating series ; 
exceedingly delicate ones are interspersed. Surface sculptured with 
numerous, equidistant, moderately elevated, concentric ridges, the 
edges of which are crenulated by decussating wrinkles, and the inter- 
spaces marked by very fine concentric lines, and so articulated with 
very short dead-white and yellowish-white ones as to appear indented 
or chased in quincunx: valves ventricose, beaks tumid, anterior lu- 
nule deeply impressed, broad cordate. Within yellowish, edge finely 
crenulate, and somewhat. blotched posteriorly. Hinge strong: anterior 
tooth parallel with the margin, elongated, and with a terminal denticle 
in the left valve: central tooth sub-bifid. 
Length an inch and three-eighths ; height an inch and a quarter ; 
breadth nine-tenths of an inch. 
Obtained at Mangsi Island, Sooloo Sea. 
In general characters allied to V. verrucosa, but is more orbicular, 
more tumid, and its sculpture far more delicate and elaborate; besides 
which it is beautifully ornamented with tent-like markings, and the de- 
ceptive quincunx appearance in the intercostal spaces, like the general 
sculpture of ‘Terebratula, caused rather by the cream-coloured opaque 
lines than by indentation, is very singular. 
Figures 537, 537 a, lateral and dorsal views of the shell. 
VENUS RIGIDA (Gould). 
Testa solida, transversa, ovato-ventricosa, inequilaterals, desuper visa 
acute ovalis, sordide alba, strits concentricis reflexis, utroque laminosis, 
et strits crassis radiantibus decussata ; decussationibus anterioribus 
punctatis ; apicibus elevatis, anteversis, contiguis: lunula lata, vix 
circumscripta : latere antico angustato, rotundato ; latere postico laté 
et oblique truncato ; margine dorsah rectiusculo ; cardine in dextra 
valva dentibus duobus fissis, in valva sinistra dente unico fisso: intus 
porcellana ; margine crenulato. 
