455 Mr. T. Scott on Cytheridea castanea. 
abundant in the sand-dunes near San Pedro on the River 
Parand and in shell-beds at San Isidro. The remains of this 
mollusk occurred mostly in the form of single valves or 
portions of valves, only in a few instances were the specimens 
complete, and in.every case the valves of the more perfect 
specimens were kept together only by the mud in which they 
were embedded. Paludistrina, a small spiral univalve, was 
also moderately frequent. ‘The remains of a small Balanus 
were occasionally observed, and one or two of the valves of 
Azara had each a Balanus adhering to them. A few Fora- 
minifera, seeds of plants, and some other things were also 
noticed; bnt the most interesting of all the fossils obtained 
was the Ostracod already referred to, viz. Cytheridea cas- 
tanea, G. 8S. Brady. 
Cytherideacastanea was described and figured by Prof. Brady 
in 1870 in ‘ Les Fonds de la Mer,’ vol. i. p. 117, pl. xii. 
figs. 19-21, pl. xiv. figs. 1, 2*. This Ostracod was dredged 
by the Marquis de Folin in the Bay of Biscay and at Port 
Said, and these two ‘places are apparently the only‘localities 
where the species has been obtained hitherto. Prof. Brady 
very kindly examined a few of the Buenos Ayres specimens, 
and is satisfied that they belong to the same species as his 
Cytheridea castanea. I may mention, however, that in all 
the specimens from Buenos Ayres which I have observed there 
isa slight depression that extends obliquely across both valves 
of the Ostracod, as shown by figures 2 and 3 (Pl. XVI.). In 
some of the specimens the depression is scarcely so con- 
spicuous as it isin others, and it is best seen when the light 
strikes lengthways across the shell. Cytheridea castanea does 
not appear to have previously been recorded from South 
America even as a fossil; its occurrence in the shell-bed at 
Buenos Ayres is therefore of interest, more especially as it 
appears to be moderately frequent in the deposit. I have 
obtained a considerable number of specimens in the sample of 
the deposit which my son brought home, and, curiously, it was 
the only Ostracod observed. 
Prof. Rupert Jones, to whom I desire to express my 
indebtedness for information concerning the fossil Entomo- 
straca of South America, has published one or two papers in 
which are described a number of forms that were obtained 
during the excavations for a new railway in Bahiat. The 
* See also the “Mon. of the Mar. and Freshw. Ostrac. of the N. At- 
lantic and N.W. Europe,” Trans. Roy. Dubl. Soc. vol. iv. ser. 2, p. 175, 
pl. xxi. figs. 3, 4 (1889). 
+ “Fossil Entom, from 8S. America,” Geol. Mag. dec. iv. vol. iv. 
pp. 259-265 & 289-298, pls. ix., x. (1897). 
