632 



MEMOIRS OF THE CARNEGIE MUSEUM. 



of the posterior retractor-scar is quite unique, but, of course, is connected with 

 the elongated shape of the shell. 



Measurements. 



Anatomy. — ^The soft parts of three specimens are at hand, but their sex is 

 not positively knoAvn. 



The structure is that of the genus Anodontites, with such modifications as are 

 caused by the elongation of the shell. The mantle-connection between anal and 

 branchial openings is a little longer than usual, the gills are extremely long and 

 narrow, and the part behind the foot, where the two inner laminae of the inner 

 gills are connected, is proportionally longer than in any other species. As indicated 

 by the scars of the shell, the posterior retractor muscle is considerably removed 

 from the adductor. 



Anal opening entirely open. Branchial opening with very small papillae. 

 Palpi comparatively long, but narrow, lower margins forming a gentle curve. Pos- 

 teriorly they are very briefly truncated, forming the posterior margins, which 

 are not connected. Structure of gills as usual, with distinct septa. I have not 

 been able to positively identify the sex of the three specimens at hand: the con- 

 dition of the gills is rather unsatisfactory, they being much torn, so that no sections 

 could be made, and from macroscopical examination (and with a lens) no indica- 

 tions of a differention of the inner gills could be detected: this, indeed, would indi- 

 cate the male sex, but my specimens are too young for one to be sure about this. 

 The inner gill, as usual begins immediately behind the palpi, and the inner lamina 

 of the inner gill is entirely connected with the abdominal sac. Foot rather long, 

 but altogether small; of course, the real shape could not be made out on account of 

 the contraction in alcohol. 



CJenus Mycetopoda D'Orbigny (1835). 

 Simpson, 1914, p. 1457. 



Characterized by very elongated, subtrapezoidal shell, which is widely gaping 

 in front. The chief characters, however, are in the soft parts. The foot is ex- 



