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 -gV inch. 



Cy there Darwiniij Brady. (Plate XII. figs. 11, 12.) 

 Cythere Darwinii, Brady, Les Fonds de la Mer. 



The specimens found in the Mauritius mud differ somewhat 

 in shape and surface-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 hamigera^ 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; inferior 

 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 Vt inch. 



Cythere hispinosa^ 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 -^ inch. 



