COERESPONDENCE. 
217 
reached by the tide. Murex erinaceus was only found in these beds, 
and rare. 
Proceeding northwards up the coast, the finest sections in Furness 
of the boulder clay are exhibited in the cliffs or sea-scarps of Moat 
Hill, Edge Bank, Beanweli Bank, and Tea Wood, with heights ran- 
ging from 50 to 90 feet. Large Carboniferous (or mountain) lime- 
stone, boulders, and angular blocks seem ready to slide down ; while 
hard detached and fallen masses become separated in time by the 
dash and spray of the tides, and strew the shore. Some of the fallen 
blocks measure 20 feet in circumference, and retain deep groovings 
on their surfaces. 
North of Ulverstone, the boulder clay reappears at Hammerside 
Point, and constitutes a hill of 60 feet altitude, with an unknown 
depth. After this, it caps the Carboniferous and Silurian rocks of 
Plumpton and Threadlow ; and then retires back and is not seen 
again on our line of coast. 
COERESPONDE]?^CE. 
On the Outer Tegument of a Section of the Genus Trigonia. 
Sir, — Permit me to direct the attention of palaeontologists to a remark- 
able feature in a section of the genus Trigonia, which indicates a wider 
separation of that section from its congeneric allies, and also an unsus- 
pected imperfection in the state of preservation of some of our most com- 
mon Jurassic testacea. It has long been known that under the name of 
Trigonia costata, some very different forms of that genus have been figured 
and described by various authors from Jurassic rocks ranging from the 
Upper Lias to the Kimmeridge Clay, including fossils from Oolitic lime- 
stones, sandy rocks, argillaceous limestones, and from soft unctuous clays. 
Considering that the materials at the disposal of authors have been derived 
from such a variety of rocks, and of localities, both European and Oriental, 
and that such numbers of the great group of the Costatae have been ex- 
amined and compared by so many authorities, it might have been expected 
that their natural-history characters had been fully ascertained, and that 
the little we have still to learn respecting them would have reference onl}'' 
to the separation or union of species, and to a more accurate definition of 
their stratigraphical range. I was therefore recently much surprised upon 
applying my pocket lens to the surface of a fine example of T. Calypso, 
D'Orb., to find that it exhibited a beautifully ornamented surface, consist- 
ing of lines of minute granules arranged vertically, and in every respect 
agreeing with the outer tegument of Gresslya, Anatina, Goniomya, and 
Myacites, amongst the Myada? or Anatinidfe. Of this latter family the 
fossil forms w^ith granulated surfaces may be separated into two divisions, 
the one having large and widely separated lines of granules, the other 
with the granules also linear, but very minute, and the rows closely ar- 
ranged ; Trigonia Calypso, from the Scarborough Cornbrash, has this lat- 
ter kind of ornamentation easily overlooked, and preserved only under the 
TOL. VII. 2 r 
