ACEPHALA. 425 
is a feebly-impressed line, vanishing as it approaches the beak; basal 
margin regularly curved; beaks anterior, protuberant, incurved, and 
contiguous. Lunule deeply impressed, large, oval, faintly striated by 
the growth of the shell; margins of the valves forming a slight ridge 
through the middle. Escutcheon strongly marked, broadly elliptical, 
extending from the beak to the extremity, and limited by a deeply- 
impressed line, its surface shining and faintly striated, and of paler 
colour. Valves sculptured by fine, sharply-cut, concentric striz, and 
covered with a thin, dark olive epidermis. Hinge denticles about fif- 
teen anterior and twenty posterior. [4J. Pp. c. ] 
Length half an inch; breadth one-fifth of an inch; height three- 
tenths of an inch. 
Dredged in Orange Bay, Cape Horn. 
It resembles N. rostrata, from Massachusetts Bay, but is shorter, 
thicker, less prolonged posteriorly, and has a strongly-marked lunule, 
which is wholly wanting in that species. It closely resembles N. 
celata, Hinds, from the Northwest Coast, which is anteriorly shorter, 
more ventricose, and sculptured all over. 
Figures 539, 539 a, two views of the shell, enlarged; 539, the 
hinge; 539¢, natural size. 
CYCLAS EGREGIA (Gould). 
T. ventricosa, transversa, oblonga, sub-equilateralis, concentricée tenui-li- 
rata; apicibus parum elevatis, tumidis; epidermide viridi-corneo, 
fusco-zonato ; plerumque C. cornee similis. 
Cyclas egregia, Goutp; Proceed. Boston Soc. Nat. Hist., ii. 292. 
Nov. 1850. Expedition Shells, 86. 
This shell is so similar to C. cornea that it would not be distinguished 
‘without careful examination. It is, however, larger, more rounded in 
outline, and more globose in form. The epidermis is less glistening, 
of a deeper green, and exhibits no traces of radiations. ‘The hinge 
ligament is shorter and more prominent. As to its beaks, furrowing, 
107 
