234 Mr. E.R. Lankester on Lithodomous Annelids. 
lime (figs. 1 & 2). On breaking off fragments of these stones 
(often so hard as to defy a heavy geological hammer), the pas- 
sages were found to extend in many cases to the depth of an 
inch, and in some cases to two inches and a half, the breadth 
of the cavity varying proportionately. The excavations in this 
case were not cylindrical, as with Sabella, but in transverse 
section presented a keyhole- or figure-of-eight outline (fig. 3). 
As seen in the drawing, they do not terminate abruptly, but 
appear to be formed by the bending-round of a ee cylin- 
drical gallery. Within these galleries, and coiled round so 
that the head and the tail both point to the aperture, many 
specimens of the worm which made them were found (figs. 5, 6). 
The worm does not lie in immediate contact with the stone, 
but the interior of the gallery is lined and its substance im- 
pregnated with a viscid secretion derived from the worm’s 
body. The partition between the two parallel passages of the 
gallery is often formed solely of this material. Boulders are 
not unfrequently found which have been entirely deserted by 
their occupants, or from which these have passed away a 
death and decay ; and in those cases the animal matter whic 
lines the excavated passages is very easily seen, and sometimes 
may be peeled off as a black carbonaceous film: 
fais the case of Sabella saxicava in mind, I was fully 
ee ei to ascribe to a chemical action the perforation of the 
ard limestone boulders by the Leucodore ; for to that genus of 
Johnston (Polydora of Bosc) the worm proved to belong. In this 
view Ireceived a quite unexpected confirmation on subsequently 
visiting White Cliff Bay, where the shore is covered with huge 
masses of chalk rounded by the sea’s washing and overgrown 
with Alge. A very large proportion of these blocks were 
perforated on the surface, just as the limestone boulders further 
west; and yet it would be difficult to find two rocks differing 
more in density and molecular structure than chalk and those 
limestone boulders. Their only resemblance was in their 
chemical composition. It was noticed that in this chalk bay 
the perforations were by no means so closely disposed: there 
was abundance of material, and therefore no cause for crowd- 
ing. Specimens of the worms from the chalk-perforations 
were obtained in great abundance, and proved identical with 
those from the limestone, whilst the galleries were identical in 
every respect, Subsequently to this, I received specimens of 
limestone from Felixstow, on the coast of Suffolk, where the 
whole shore is clay, masses of soft clay being exposed at low 
tide, overgrown with weed and abounding with life. Not a 
single Leucodore-perforation is to be found in this clay, though 
Pholades and Hunice are abundant in it. Here and there in 
