Mr. T. Scott on Cytheridea castanea. 455 



abundant in the sand-dunes near San Pedro on the River 

 Parana 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 tilings were also 

 noticed ; but the most interesting of all the fossils obtained 

 was the Ostracod already referred to, viz. Cytheridea cas- 

 tanea, G. S. Brady. 



Cytheridea castanea was described and figured by Prof. Brady 

 in 1870 in ' Les Fonds de la Mer,' vol. i. p.*117, pi. xiii. 

 figs. 19-21, pi. 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 

 is a slight depression that extends obliquely across both valves 

 of the Ostracod, as shown by figures 2 and 3 (PI. XVI.). In 

 some of the specimens the depression is scarcely so con- 

 spicuous as it is in 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. 1 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. 



Prot. 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 Bahia f. The 



* See also the " Moo. of the Mar. and Freshw. Ostrac. of the N. At- 

 lantic and N.W. Europe," Trans. Eoy. Dubl. Soc. vol. iv. ser. 2, p. 175 

 pl.xxi. figs. 3,4(1889). 



t "Fossil Entoin. from S. America," Geol. Mag. dec. iv. vol iv 

 pp. 259-205 & 289-293, pis. ix., x. (1897). 



