froiin 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 -^ inch. 



Loxoconcha Lilljeborgii^ no v. 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 ^ inch. 



h, Lilljehorgn is in general appearance not very unlike a 

 West-Indian species {L. 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 alKed form. 



EXPLANATION OF THE PLATES. 



Plate XII. 



Fig. 1. Cythere demissa, seen from left side. ) 



Fig. 2. Tlie same, from above. (. v 4.0 



Fig. 3. Cythere convoluta, seen from left side. C '^'*^' 



Fig. 4. The same, from above. j 



Fig. 5. Cythere hamigera, seen from right side. ) 



Fig. 6. The same, from above. I x50. 



Fig. 7. The same, from front. \ 



Fig. 8. Cythere bispinosa, seen from left side." 



Fig. 9. The same, seen from below. 



Fig. 10. The same, from front. 



Fig. 11. Cythere Darioinii, from left side. )■ x 40. 



Fig. 12. The same, from below. 



Fig. 13. Cythere fumata, from left side. 



Fig. 14. The same, from below. 



