154 Contributions to Indian Malacology. [No. Z, 
of the shell, prominence of the umbones, shape of the muscular im- 
pressions, colour of the nacre, characters of the epidermis, &c. vary 
ad infinitwm—in short that species must be described like genera and 
grouped around types, not distinguished by characters. 
I see from a notice in the Paris Journal de Oonchyliologie that, in 
the same volume of the American Journal of Conchology, Mr. Conrad 
proposed a new genus Zrigonodon for Monocondylea crebristriata of 
Anthony, from which, as I have stated above, Anodonta inoscularis, 
Gould, is at the best but dubiously separable specifically. But the 
last named shell is the type of Gould’s genus Psewdodon, and Gould 
himself suggested the identity of that genus with D’Orbigny’s Mono- 
condylea.* Unless Mr. Conrad has procured the animals of the Pegu 
forms, and shewn them to be distinct from those of South America, 
(and I scarcely think he can have done so,) I cannot believe that any 
useful object is attained by inventing these geneyic appellations. Even 
if Trigonodon be not Pseudodon over again, (Mr. Conrad appears to 
have already furnished one synonym before for Pseudodon, viz. 
Monodontina,) there has been no distinction of any generic value 
shewn between the shells of Burmese and Malay species of Monocon- 
dylea and those of S. America; and bearing in mind that there are 
some genera of more restricted distribution than those belonging to 
the Unionide, e. g. the Tapir, and amongst Mollusks, Cyclophorus 
and Megalomastoma, common to .the two regions, it would, I think, 
be more scientific to examine the animals of the Burmese shells allied 
to Monocondylea, before founding new genera to comprise them. 
There is of course the possibility that Mr. Theobald may have been 
misinformed as to the respective names of the two species, and that 
the type of Tmgonodon is the form I have referred to Monocondylea 
Vondenbuschiana, I can only add that the specimens of the same shell 
from the same locality sent to me by Mr. Theobald, do not differ 
more from Kiister’s figure of V. d. Busch’s original specimen of JZ. 
Vondenbuschiana in Martini and Chemnitz, than that figure does from 
Lea’s. 
Unio Praurnsis, Anthony. 
American Journal of Conchology, Vol. I. 
I cannot learn what species has been thus named I hope to be 
able to refer to the volume before long and to return to the subject. 
* Ot. Conch., p, 194, 
