On the Permian System of Durham and Northumberland. 463 



the gills are easily shed. The Triptera columella, when first 

 taken, swims vigorously about, and protrudes a proboscis which 

 curves downwards, which it frequently rapidly retracts into 

 the interior of the body and as rapidly exserts again. The 

 greater majority of small oceanic Crustaceans, like a large num- 

 ber of other animals which inhabit the high seas, are of a deep 

 blue colour, which, however, changes to a bright red when the 

 animals are placed in spirit. 



I remain. Gentlemen, 



Your obedient Servant, 



Arthur Adams. 



XXXVI. — Notes on the Permian System of the Counties of Durham 

 and Northumberland. By Richard Howse, South Shields. 



[Concluded from p. 312.] 

 Gasteropoda. 



33. Chiton Loftusianus, King. — The general form of this 

 Chiton, and the size it attained, are at present unknown, for 

 the plates have never been found articulated together. It may, 

 perhaps, be inferred, from the size of the plates that have oc- 

 curred, that it was rather a small species than otherwise. 



The marginal outline of the first and last plates is semicir- 

 cular, that of the second unguiform. The third plate, supposed 

 by the author of the ' Perm. Mon.^ to be the second, is some- 

 what triangular ; the fourth is slightly furcated ; and the other 

 three, assuming it had eight altogether, are oblong or strap- 

 shaped in marginal outline. The second, third and fourth 

 plates are broad and very oblique ; the fifth, sixth and seventh, 

 narrow and transverse. The posterior plate, which is not ' ca- 

 jmliform,' but half-limpet-shaped, has its apex or mucro produced 

 to a fine point. Seen in profile, all the plates, excepting the 

 first or head-plate, are curved towards the posterior margin, 

 considerably elevated along the dorsal line, and pressed down 

 steeply on each side towards the lateral margin. The lateral 

 areas of the intermediate valves, excepting the second, are large 

 and distinctly defined. Occasionally a small sulcation or furrow 

 may be seen on each side of the dorsal ridge, but this seems to 

 be rather an accidental than a specific character. The entire 

 surface of all the plates is minutely granulated or shagreened, 

 and the striae of growth are very distinct on the dorsal as well 

 as on the lateral areas. The interior of the valves is minutely 

 pitted or granulated. The apophyses or processes of attach- 



