COREESPONDENCE. 
53 
relat. vi. et x. p. 74, fig. 2. Quicquid horum sit, majori certitudine dili- 
gentissimus Buttnerus, p. 218, avium nidos et ova in Thuringise lapici- 
dina tofacea inventa his verbis notatu dignis allegat : Ich hekomme noch- 
maJilige Versicherung " etc. 
MTTILUS SPATRULATUS, A NEW CEETACEOUS 
SPECIES. 
By H. Seeley, E.G.S. 
A flint cast of a Mytilus has been obtained from the g^ravel of 
Barnwell, near Cambridge, by Mr. Percevall. B.A., Trin. Hall, and 
entrusted to me for description. 
Form elongated and narrow, attenuated anteriorly, with valves 
deep, and longitudinally striated. The anterior outline of the lips is 
straight, that of the posterior side a gentle curve, which is somewhat 
straightened towards the apex. The shell is about three times and 
a half as long as wide, and widest below the middle. The lateral out- 
line of the valves is lanceolate, the greatest height being in the an- 
terior third. 
From the umbones the [subacute] line of inflation ascends, and 
curves posteriorly, so as to overhang the hinge. It then becomes 
rounded, and curves into the middle of the shell. The sides descend 
from it nearly straight. So, on the anterior side of tlie umbonal end, 
the sides slope somewhat away from tlie lips, penthouse-like ; while 
on the posterior side they slope somewhat together, forming a shal- 
low trough. The height of the shell is more than twice its trans- 
; verse diameter. 
' The whole is marked with numerous, close, very fine, longitudinal 
striae, which appear to be crossed by fine striae, coincident with the 
j lines of growth, but wider apart. The lips are dentated. 
I This remarkable form, the first Mytilus yet noticed from the En- 
glish chalk, must have had a very thin shell, since the faintest exte- 
rior ornament, seems all preserved on the flint cast. 
It is constricted at intervals by rugose bands of growth. 
I The high valves, laterally compressed form, straight anterior side, 
and very compressed umbonal end, will readily distinguish this from 
every other striated cretaceous species. All the forms yet observed 
j in the chalk are striated. 
COREESPONDENCE. 
Spiral Planetary Orhits. 
Dear Sir, — As a regular subscriber to the 'Geologist,' aud one interested 
in its success, I doubt not you will pardon me for a few remarks upon your 
editorial articles in the last two numbers. 
