MOLLUSCA. 695 
C. borealis (Conrad), New England, and C. ventricosa (Gould), California. 
Am. Joiirn. Conch, iii. p. 191. 
UnioniM. 
E. A. Forel (Inaugural Dissertation, see above, p. 498) pub- 
lishes some interesting and very curious observations on the 
first stages of development of Anodonta. The eggs are found 
within the gill-pouches of the adult animal from July to January, 
the cleavage process taking place in autumn. When expelled 
from the gill-pouches, they sink slowly in the water; the very ten- 
der enveloping membrane is tom by slight contact with the bot- 
tom; the slicll of the hatched young animal gapes widely, the 
adductor muscle (which in this stage of growth is single) not 
being able to keep the valves together. A single long byssal 
thread is thrown out, which plays in the water. The organs of 
circulation and digestion are not yet developed. From J anuary 
to April the author found young Anodontm in this stage often 
on tlie gill-covers, lips, and fins of fishes, especially Leuciscus 
and Gobio ; they were enclosed in a sort of cyst, consisting of 
epithelial cells. He supposes that the byssal thread serves to 
take hold of the fish, and that the spines, which exist in that 
stage on the edge of the valves, are of essential use to the mol- 
lusks in fixing themselves to its body. The further development 
could not be observed by the author. 
Unio, A monograph of this genus is continued in the late Mr. Reeve’s Con- 
chologia Iconica, parts 266-265. Critical remarks concerning several species 
contained in this work [probably by Lea], in Am. Journ. Conch, iii. p. 246. 
Vnio hatams (Lam.), from the Lake of Geneva, described and figured by. 
Brot, Etudes sur les Nayades du lac L^man, p. 49, pi. 9. 
Unio mancus (Lam.) regarded by Moquin-Tandon as a variety of U. ha* 
tavus, is treated of by Drouet, Moll. C6te d’Or, p. 104. He does not come to 
a final conclusion. He had specimens from the same rivulet (Dree) which is 
given by Lamarck as locality ; and no other form of Unio occurs in it. 
U. nanns (Lam.) is a diminutive form of the same species, living in the Sa6ne 
river ; this name, as well as U, amnicus (Ziegl.), will pass into the syno- 
nymy of U. mancus, if the species be reintroduced. , 
Thiio lamhottei and ryckholtii, spp. nri., Malzine, Faune Malacol. Belg. p. 32, 
pi. 2. figs. 3, 4, and figs. 1, 2, in the river Meuse.— U. rohianoi, sp. n., ibid, 
p. 33, pi. 1. figs. 1-4, from a streamlet near Harvengt, in Belgium [may be 
safely referred to U. litoralis~\, 
Unio danielis, sp, n., Gassies, Malacol. Aquit. I c. p. 26, fig. 8. Allied to 
U pictorum, distinguished by radiating strife and the form of the cardinal 
and lateral teeth. Several pools in the intralittoral region to the left of the 
Garonne, in company with Anodonta piscinalis, 
Unio maccartliyanus, sp. n., Bourguignat, Moll. Nouv. fasc. vil. 1866, p. 
220, pi. 34. figs. 8-11, Algeria. 
Unio grayanm (Lea), Ussuri River, a tributary of the Amur; U, picio-‘ 
, rum (L.), Ussuri and Amur, Schrenck, 1. c. pp. 694-699; a very large speci- 
men of the first figured, pi. 27. figs. 1-3. 
