NORTHUMBERLAND AND DURHAM. 271 



which projects into tlie cavity of the shell, and forms an advanced 

 point of attachment for a visceral, or perhaps for the pedal muscle. 

 The general configuration of this shell also suggests that it was 

 a burrowing mollusk. It is very doubtful whether this species 

 belongs to the genus Edmondia, De Koninck. 



It is not a very common species in the shell-limestone of Tun- 

 stall, Humbleton, &c., and occurs also in the equivalent deposit 

 of Possneck. 



27. TELLINA, Litm. 

 1. T. DuNELMENsis, Ilowse. PL XL figs. 14, 15. 



" Shell elliptical; heciks small, not prominent, situated near the 

 anterior end, which is somewhat rounded; posterior elongated, more 

 acute than the anterior; two cardinal teeth in each valve.'''' 



The specimens of the shells which I have been able to examine 

 do not permit much to be added to the above characters. The 

 specimen figured in the " Perm. Mon." is imperfect, for the pos- 

 terior of this shell is rather acute, perhaps not quite so much so 

 as in the figures, PL XI. figs. 14, 15. The valves are generally 

 found together, and spread out, which is the case also with several 

 other Permian species. It shows that they were provided with 

 a very strong ligament. 



In the shell-limestone at Humbleton. 



GASTEROPODA. 

 28. CHITON, Linn. 



1. C. LoFTusiANUS, King. 



The general form of this Chiton, and the size it attained to, are 

 at present unknown, for the plates have never been found articu- 

 lated together. It may, perhaps, be inferred, from the size of 

 the plates that have occurred, that it was rather a small species 

 than otherwise. 



The marginal outline of the first and last plates is semicircular, 

 that which I suppose to be the second is rather unguiform. The 

 third plate, supposed by the author of the " Perm. Mon." to be the 

 second, is somewhat triangular; the fourth is slightly furcated; 



