454 Mr. T. Scott on Cytheridea castanea. 



from Tomdcelys, Co. Limerick, Ireland. The specimen lacks 

 the body-chamber, the anterior end of the specimen being the 

 surface of the last septum. Although this septal surface is 

 incomplete, 'there is sufficient to show clearly that the species 

 belongs to the genus Brancoceras. This was the only 

 example known to De Koninck. 



Affinities and Differences. The closed umbilicus, the wide 

 umbilical depression, the ornaments of the test, and the form 

 of the suture-line at once distinguish the present species both 

 from Glyphioceras striatum, J. Sowerby, sp., and Glyphio- 

 ceras crenistria, J. Phillips, sp. 



LX. — Note on the Occurrence of Cytheridea castanea, G. S. 

 Brady, in a Surface-deposit in the Vicinity of Buenos Ayres, 

 South America. By Thomas Scott, F.L.S. 



[Plate XVI.] 



Darwin, when describing the surface-geology of the Pampas 

 in his ' Geological Observations on South America,' alludes 

 to the occurrence of shell-bearing sand-dunes on the shores of 

 the Kio de la Plata and elsewhere in the province of La Plata. 

 Numbers of these dunes are to be found in the vicinity of 

 Buenos Ayres, especially towards the shores of the estuary of 

 the Plate. The dunes referred to are generally more or less 

 covered with vegetation, but in some instances, where the 

 vegetation is displaced, a shell-bed a few inches thick and of 

 a darker colour and firmer consistency than the sand is seen 

 to stretch across each of the dunes in a nearly horizontal 

 position. It is in this shell-bed that the Cytheridea was 

 obtained that forms the subject of this note. 



Buenos Ayres, being an important seaport, is frequently 

 visited by ships trading to South America. My younger son, 

 Mr. John Scott, is a marine engineer, and his ship happened 

 to be at Buenos Ayres for several days during January last 

 year (1898). My son is interested in natural history, and, 

 being ashore, he took the opportunity to examine a few of 

 the sand-dunes in the vicinity of the harbour of Buenos Ayres 

 and also to collect a quantity of the material in which the 

 shells are embedded. In collecting this material he first 

 scraped away the surface-matter, then, digging well into the 

 shell -bed, removed what he considered to be a fair sample of 

 the material ; this he brought home on his return to England. 

 I made a careful examination of the material my son had 

 brought to me, and obtained from it a number of different 

 kinds of fossils ; the most common species obtained was Azara 

 labiata, d'Orb., a bivalve mollusk mentioned by Darwin as 



