SAILORS' SUPERSTITIONS. 



103 



they allow no questions to be asked, they will not dip 

 a pot for water into the lake, fearing to be followed 



to the Danube ; for the American shells referred to it are probably, or, I may 

 say, certainly distinct. It agrees with the Danubian shells in the extreme 

 obliquity of the aperture, and differs in the width of the umbilicus, which in 

 the European species is nearly concealed by the callous columellar lip. 



In the Upper Eocene Tertiaries of the Isle of Wight there are several 

 estuary shells, forming the genus Globulus, Sow., whose affinities are uncer- 

 tain, but which resemble Lithoglyphus. 



The lake Tanganyika (situated in lat. 3° to 8° S. and long. 30° E.), which 

 is several hundred miles in length and 30 to 40 in breadth, seems entirely 

 disconnected with the region of the Danube : but the separation may not al- 

 ways have been so complete, for there is another great lake, Nyanza, to the 

 northward of Tanganyika, which is believed by Speke to be the principal 

 source of the Nile. 



The other univalve is a Melania, of the sub-genus Melanella (Swainson), 

 similar in shape to M. hollandi of S. Europe, and similar to several Eocene 

 species of the Isle of Wight. Its colour, solidity, and tuberculated ribs give 

 it much the appearance of a small marine whelk (Nassa) ; and it is found in 

 more boisterous waters, on the shores of this great inland sea, than most of 

 its congeners inhabit. 



1. Iridina (Pleiodon) Spekii, n. sp. (PI. XL VII. fig. 2.) 



Shell oblong, ventricose, somewhat attenuated at each end : base slightly 

 concave ; epidermis chestnut brown, deepening to black at the margin ; an- 

 terior slope obscurely radiated ; hinge-line compressed in front and tubercu- 

 lated, wider behind and deeply wrinkled. 



Length 4f, breadth 2, thickness If inches. 



Testa oblonga, tumida, extremitatibus fere attenuata, basi subarcuata ; epi- 

 dermide castaneo-fusca, mar ginem versus nigricante; linea cardinali antice 

 compressa tuberculata, postice latiore, paucis rugis arata. 



2. Unio Burtoni, n. sp. (PI. XL VII. fig. 1.) 



Shell small, oval, rather thin, somewhat pointed behind ; umbones small, 

 not eroded; pale olive, concentrically furrowed, and sculptured more or less 

 with fine divaricating lines ; anterior teeth narrow, not prominent ; posterior 

 teeth laminar; pedal scar confluent with anterior adductor. 



Length 12, breadth 8|, thickness 5^ lines. 



Testa parva, ovalis, tenuiuscula, postice subattenuata ; umbonibus parvis, 

 acuminatis ; epidermide pallide olivacea ; valvis lineolis divaricatis, decuss- 

 atum exaratis ; dentibus cardinalibus angustis, Jiaud prominentibus. 



3. Lithoglyphus zonatus, n. sp. (PI. XLVIL fig. 3.) 



Shell orbicular, hemispherical ; spire very small ; aperture large, very ob- 

 lique ; umbilicus wide and shallow, with an open fissure in the young shell ; 

 lip continuous in front with the umbilical ridge ; columella callous, ultimately 



h 4 



