from the Mauritius. 183 
straight. Outline, as seen from above, subcuneiform, widest 
behind the middle, obtusely mucronate in front, broadly 
rounded and centrally emarginate behind; greatest width 
equal to half the length. End view broadly ovate. Shell 
covered with large, distant, subcircular or obscurely angular 
pittings, and raised behind the middle into a rounded emi- 
nence. Colour white. Length 34 inch. 
Loxoconcha Lilljeborgit, nov. sp. (Plate XIII. figs. 11-15.) 
Carapace of the female, as seen from the side, subrhomboidal, 
highest in the middle; greatest height equal to nearly two- 
thirds of the length: anterior extremity obliquely rounded ; 
posterior produced above the middle into a short (often bi- 
dentate) process: superior margin arched, highest near the 
middle, behind which it is gently sinuated ; inferior sinuated 
in front, protuberant behind. Outline, as seen from above, 
subovate or obscurely pentagonal, widest about the middle, 
pointed in front, strongly mucronate behind; greatest width 
much less than the height. Shell marked throughout with 
large oblong pittings, which are arranged in concentric 
rows, and tend to form furrows by their coalescence on the 
ventral surface: a conspicuous angular protuberance near 
the postero-dorsal angle of each valve. Length #5 inch. 
L. Lilljeborgit is in general appearance not very unlike a 
West-Indian species (Z. avellana) described by me in Trans. 
Zool. Soc. vol. v.; but the present species is well characterized 
by the posterior dorsal protuberance, and is, moreover, of very 
different outline when seen from above or below. L. affinis, a 
Mediterranean species, is also a nearly allied form. 
EXPLANATION OF THE PLATES. 
PuatTE XII. 
. Cythere demissa, seen from left side. 
The same, from above. 
. Cythere convoluta, seen from left side. 
. The same, from above. 
Cythere hamigera, seen from right side. 
. The same, from above. x 50. 
. The same, from front. 
. Cythere bispinosa, seen from left side. ) 
. The same, seen from below. 
Fig. 10. The same, from front. 
Fig. 11. Cythere Darwinit, from left side. 
Fig. 12. The same, from below. 
Fig. 13. Cythere fumata, from left side. 
Fig. 14. The same, from below. 
x 40. 
SY'S'S'S'S'S'S 
OO ~7 o> OUR CO DO 
-x 40. 
‘SN 
