COBfiESPONDBSCE. 



•53 



relat. vi. et x. p. 74. fig. 2. Quicquid hornm sit. majori certinidine dili- 

 gentissimns Buttxzeus, p. 21S, avium nidos et ova in Thuringise lapici- 

 dina tofacea inventa his verbis notatu dignis allegat : Ieli bekomme nocli- 

 maJdige Yersklierang" etc. 



MTTIL US SPA IH UL AT US. A XEYT CRETACEOUS 

 SPECIES. 



By H. Seeley ; F.G.S. 



A flint cast of a Mytilus has been obtained from the gravel of 

 Barnwell, near Cambridge, by Air. Peroevall. 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 the umbonal end, 

 the sides slope somewhat away from the lips, penthouse-lite : 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 

 stria?, which appear to be crossed by fine striae, coincident with the 

 lines of growth, but wider apart. The lips are dentated. 



This remarkable form, the first Mytilus yet noticed from the En- 

 glish chalk, must have had a very thin sheil, since the faintest exte- 

 rior ornament seems all preserved on the flint cast. 



It is constricted at intervals by rugose bands of growth. 



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 

 in the cha.k are striated. 



CORKESPONDEXCE. 



Spi?'aJ Planetary Orbit*. 



Dear Sir. — As a regular subscriber to the 'Geologist,' and 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. 



