320 Mr. Hoce on the Marine Production 
black specks situated on the front, which I concluded without 
doubt to be its eyes. 
Tas. IX. Fig. 1. represents, in its natural size, the under 
surface of a portion of this substance, broken through the middle 
of a perfect specimen, at right angles to its edge; and shows 
plainly the arrangement of the shells, which are expressed by 
the shaded parts of the drawing. 
Fig. 2. is a similar section, somewhat magnified, to exhibit 
more clearly the forms of the cells, contained between the two 
layers of conglutinated sand. 
Fig. 3. represents one of the minute shells in its natural size. 
Fig. 4. is a back view of the same, highly magnified. 
Fig. 5. is a young shell of Nerita glaucina, seen also from the 
back; which is here introduced to be compared with the last 
figure. And for the same reason, Fig. 6. shows the aperture 
and umbilicus of the shell, Fig. 5., in order to prove the exact 
resemblance which it bears to Fig. 7., another small shell, re- 
presented from the side of the aperture and umbilicus, and mag- 
nified on the same scale as Fig. 4. 
Fig. 8. is the same as Fig. 7. in its natural size. 
The exact similitude of these small testaceous bodies to the 
livid Nerite, induces me to believe that they are the young of 
that species. 
This substance is sometimes found with a small hole in each 
of the cells opening on the under surface (as at Fig. 1.): this 
hole is formed by the shell contained in the cell, which, when 
sufficiently grown, forces its way through the under coating of 
sand, and thus exchanges its former abode for the shore. 
If a part of this production, when perfectly dry, be immersed 
in muriatic acid, it will slightly effervesce, and the calcareous 
particles will be dissolved; and others which are indissoluble, will 
be 
