148 Transactions.— Zoology. 
Arr. XVIII.—On the Fresh-water Lamellibranchs of New Zealand, 
By Proressor F. W. Huron. 
[Read before the Philosophical Institute of Canterbury, 13th October, 1881.] 
Plate IT. 
Union. 
In the second volume of Dr. Dieffenbach’s “Travels in New Zealand” 
(London, 1843) Dr. Gray described two species of Unio, brought to England 
by Dr. Dieffenbach and Dr. Sinclair. These he called U. menziesii and U. 
aucklandica, They are distinguished by the first being high and compressed, 
the posterior lateral teeth crowded, the inner anterior tooth of the right 
valve large, thick, ovate, rugose, and the other teeth small and compressed. 
He also distinguished a variety which was more elongated, and rounder 
behind, and the posterior lateral teeth not so elevated. The second species 
is thick, the cardinal teeth low, blunt, oblique, and the posterior lateral teeth 
laminar, and far off. These species were afterwards figured by Reeve in his 
Conchologia Iconica. 
In 1850 Mr. A. Gould published in the « Proceedings of the Boston 
Society of Natural History” a description of another species from Auckland, 
under the name of U. lutulentus, and this was afterwards figured in the 
** Mollusea of the United States Exploring Expedition,” and also by Reeve. 
I have not seen Gould’s description or his figure, but, according to Reeve, 
the shell is rudely longitudinally plicated. 
In the ‘‘Malakozoologische Blatter” for 1861 Dr. Dunker described a U. 
hochstetteri, brought to Germany by Dr. v. Hochstetter from the River 
Waikato and Lake Taupo, distinguished by being “ very indistinctly sub- 
verrucose in the middle. This also is figured by Reeve, and shows & 
shell very much truncated behind, the length being only 1-4 times the 
height. 
In the ‘‘ Mollusca of the Voyage of the Novara” Dr. Dunker also described 
and figured a U. zelebori. This is rather an elongated shell, the length 
being twice the height, and with the cardinal teeth compressed, acute, and 
crenated. Having examined a large number of specimens from various 
parts of New Zealand I have come to the conclusion that neither the shape 
of the shell nor the form of the teeth ean be depended upon for specific 
characters, indeed hardly two individuals can be found alike ; and from the 
River Avon, at Christchurch, I have obtained many individuals, living 
together, which combine in various ways the characters of menziesii, auck 
landica, and zelebori, and the animal in all is alike. U. lutulentus is, 1 
