392 DK, H, L. JAMESON OK THE [Apr. 16, 



very inconstant form. The radius from the umbo to postero- 

 veritral angle of shell is usually moi-e distinct than the others and 

 often different in colour. No two of the ten examples in the 

 Museum are similarly coloured, all colours — black, brown, purple, 

 red, pink, white, and yellow — being represented in all possible 

 combniations. 



The interior of the lip is wliite with scattered red blotches, or 

 golden yellow with dark brown markings, or cream-coloured with 

 pale brown markings, or black with irregular white markings. 



The nacre has the yellowish-green tint characteristic of M. 

 panasesce. 



Measurements. Hinge 30 mm. ; greatest antero-post. measure- 

 ment 40 ; do. nacre 30 mm. Greatest dorso-ventr. measurement 

 35 mm. ; do. nacre 25 mm. Greatest antero-posterior measure- 

 ment is very nearly on the ventral margin in some specimens. 



The shell shows a strong tendency for the postero- ventral angle 

 to be drawn out somewhat, as in Pteria s. s. or Electroma. This 

 character, coupled with great obliquity and convexity, extra- 

 ordinarily rich coloration, and unusual length of the ventral 

 margin, should suffice to distinguish this somewhat aberrant 

 species. 



Geographical Distribution. 10 specimens in B. M., 1885.9.19, 

 nos. 13-22 ; found attached to pumice-stone floating off Mauritius 

 {Robillard). 



Species or fncertain position. 

 Species 28, MAEaAEiTiEERA nigea. 



Avieula nigra, Gould, 1850, p. 309. Singapore. 

 Avicula nigra, Gould, 1852, pp. 438-9, pi. 40. fig. 554. 



Species 29. Maegaeitieeea yidua. 



Avicula vidua, Gould, 1850, p. 309. Fiji. 

 Avicula vidua, Gould, 1852, p. 439, pi. 39. fig. 553. 



Species 30. Margaritifeea glabea, 



Avicula glabra, Gould, 1850, p. 310. New Zealand. 

 Avicida glabra, Gould, 1852, pp. 442-3, pi. 39. fig. 552. 



Species 31. Maegaeitifera piiACUNoiDEs. 



Avicula placunoides, 'Ree\e, 1857, sp. 68. Australia. Type in 

 B.M. 



Species 32. Margaeitifeea tegflata. 



Avicula tegulata, Eeeve, 1857, sp. 17. Moreton Bay, Queens- 

 land. Type in B.M. 



Species 33. Maegaeitifeea lacunata, 



Avicula lacunata, Eeeve, 1857, sp. 29. New Holland. Type in 

 B.M. ' ' 



