PERFORATIONS OF MARINE ANIMALS. 49 
creatures as live there could improvise means to pierce it, 
whilst at the same time it would secure perfect insulation of 
the telegraph-wire, caoutchouc is that material,’ have not been 
verified. 
The work of the burrowing crustaceans, however, is quite 
overshadowed by the far more serious encroachments which the 
boring shell-fishes are capable of making in timber and similar 
substances, as well as in rocks of diverse kinds. 
Many are probably familiar with the perforations of the 
various species of Pholas on rocky shores, for they bore in sand- 
stone, gneiss, mica-schist, limestone, chalk, lava, aluminous 
shale, peat, wood, and even wax. All round the western and 
Castle rocks at St. Andrews, as well as at many parts of the 
eastern rocks, the shale, limestone, and sandstone are extensively 
perforated by Pholas crispata, and less frequently by P. candida, 
while the calcareous rocks and chalk of the southern shores of 
England abound with another species, viz. P. dactylus. All 
these are occasionally used as food, like their southern congener 
of the coasts of Italy, viz. the date-shell (Lithodomus). Pholas 
candida seems to bore at St. Andrews in rocks somewhat beyond 
low water, for it was only when the blasting operations of 1896 
connected with the drainage works took place that fine examples 
of this species were thrown in numbers on the beach, and collected 
by Dr. Mactier.* Gastrochena, again, mostly frequents the 
shells of other mollusks such as Pecten on the southern coasts, 
and lines its tube with a shelly secretion. It likewise bores in 
granite and limestone, yet its external horny layer presents 
slight evidences of friction—indeed, only at one end. 
The effect of the ceaseless boring of rocks all round the 
shores of Britain by Pholades, Saxicara, and other forms must 
be noteworthy, since at and beyond low water the sea, especially 
in storms, will break up the much perforated ledges of rock, 
liberating the adult as well as the smaller Pholades as food for 
other marine animals, but not before an abundant series of larve 
carry the operations to fresh sites, which range from half-tide 
mark to the laminarian region, and probably beyond. No effort 
* This rare mechanical cause is analogous to the action of certain remark- 
able storms which once in fifty years may send such species as Thracia 
conveza on the beach at St. Andrews, where it was also collected by Dr. 
Mactier. 
