from the Mauritius. 181 
than half the length. Surface of the valves covered with 
closely set angular excavations, arranged in a subradiate 
manner, and bearing just within and parallel to the anterior 
margin a prominent raised ridge. Colour smoky brown. 
Length 35 inch. 
Cythere Darwinti, Brady. (Plate XII. figs. 11, 12.) 
Cythere Darwin, Brady, Les Fonds de la Mer. 
The specimens found in the Mauritius mud differ somewhat 
in shape and surtace-markings from the type specimens, which 
were collected in the sea of Java. I have therefore thought 
it desirable to give a figure. It will be seen that the outline 
here is less flexuous ; but the essential characters of the species 
appear to be the same. 
Cythere hanugera, nov.sp. (Plate XII. figs. 5-7.) 
Carapace tumid, densely spinous. Seen from the side, sub- 
quadrangular, highest over the anterior hinge-joint ; greatest 
height equal to more than half the length: anterior extre- 
mity broad and well rounded; posterior narrow, scarcely 
rounded: superior margin straight, rather steeply sloping, 
with a slight sinuation in front of the middle; interior 
nearly straight. Seen from above, the outline is ovate, 
widest behind the middle, broadly rounded behind, obtusely 
pointed or subtruncate in front; greatest width scarcely 
equal to the height. Surface densely clothed with short 
tubercular spines, which towards the dorsal margin are 
often developed into sharp, reflexed, hook-like processes. 
Length ;5 inch. 
Cythere bispinosa, nov. sp. (Plate XII. figs. 8-10.) 
Shell tumid. Seen from the side, subtrapezoid ; greatest height 
in front of the middle, and equal to more than half the length : 
anterior extremity obliquely rounded, bordered with a thin 
squamous lamina; posterior emarginate above, produced 
below the middle into a prominent subdentate beak: supe- 
rior margin sinuated in the middle, suddenly sloping at 
each extremity ; inferior slightly convex in the middle, and 
sinuated toward the extremities. Seen from above, ovate, 
widest behind the middle; extremities broadly rounded, 
mucronate. End view almost rectangular, with irregularly 
jagged margins. Surface of the valves uneven, beset with 
numerous small tubercles, and bearing three sharply cut 
longitudinal crests, that within the ventral margin termi- 
nating behind the middle in a sharp projecting spine. 
Length 5; inch. 
