30 THE. NAUTILUS. 
spicuous at the margins of the impressed ray; posterior cardinal 
margin nearly straight, anterior ditto evenly rounded ; interior por- 
cellanous white, the pallial sinus not reaching the middle vertical 
line of the shell, broad and rather rounded ; ligamental fosset large, 
cuplike; anterior teeth V-shaped, about 22 in number, strong and 
prominent; posterior teeth similar, and forming an equally long line 
but only 18 in number, the posterior cardinal margin showing a 
long narrow impressed area very feebly marked ; length of shell 
32: beak from anterior end 12; vertical from beak to base 17; 
max. diameter 15 mm. 
Habitat U.S. Fish Com. Station, 3202, in 382 fathoms green 
mud, Monterey Bay, California, bottom temperature, 41° Fahren- 
heit. 
This fine shell recalls Y. thracieformis, but is smaller, without the 
angularity of that species and proportionately more solid. It was 
dredged by the U. S. Steamer Albatross, several years ago. It is 
probably a deep water species exclusively at least in the latitude of 
California. The types are in the, U.S. Nat. Museum, 106,972. 
NOTES ON THE GENERA OF UNIONIDEZ AND MUTELIDZ. 
BY H. A. PELSBRY. 
In the June number, p. 20, a list of the-genera of Unionide and 
Mutelide recognized by Dr. v. Ihering is given. It should be noted 
that by inadvertence Pleiodon Conr. is given as a genus, but Iher- 
ing considers it a synonym of Jridina. The genus Pseudodon Gld. 
was omitted after Cristaria Schum.’ 
Attention should also be directed to the fact that the name Cas- 
talia Lam., 1819, is preoccupied in Vermes by Savigny, 1817 (Sys- 
téme des Annelides). Probably TerraPLopon Spix, 1827 can be 
used in this case as a substitute. 
For Aplodon Spix (preoc. by Rafinesque in Pulmonata), may be 
substituted SprxoconcHa. 
Lea’s name Plagiodon (1856) seems also to be preoccupied (by 
Dumeril in Reptilia, 1853), and the group may therefore be called 
IHERINGELLA, Lea’s species isocardioides being the type. 
‘The Editor fears that these errors may have been due to his own hasty proof- 
reading, rather than to defects in the original MS. 
