34 FAUNA OF THE CORNBRASH. 



Bean " N., imperfect," and, tliongli listed, has not been recognised in any Yorkshire 

 specimen, unless it be represented by the only Nautilus in the Leckenby Collection, 

 which resembles it somewhat, but is nevertheless otherwise placed. 



N. inflatus is recorded by Professor Buckman from Fairford, and by Mr. Horton 

 from Witney, but the corresponding specimens have not been discovered. Never- 

 theless, as the species is quite distinct from others recorded, and as under the 

 name N. subinflatus Messrs. Foord and Crick have recognised a species from the 

 Inferior Oolite below and from the Upper Oxfordian above, it is quite possible that 

 a similar form might occur in the intervening stratum, and these records be the 

 only indication we have of it. 



N. lineatus is recorded by Hull from the Witney district, but no corresponding 

 specimen is to be seen ; we cannot therefore say what species was intended. As 

 the general aspect is not far removed from the young of N. truncatus, and the 

 latter also frequently shows the median or " normal " line, it is not improbable 

 that the latter species was intended. 



Nautilus truncatus, Sowerby. Plate II, figs. 1, 2. 



1816. Nautilus truncatus, J. Sowerby, Min. Couch., vol. ii, p. 49, pi. cxxiii. 

 1900. — — G. C. Crick, Geol. Mag. [4], vol. vii, p. 514. 



Not " N. truncatus Sow.," D'Orbigny, Terr. Jur., pi. xxxix. 



Type. — " Thick, flatted, plain, umbilicate, back flat, mouth elongated, four- 

 angled, siphuncle nearest to the inner margin of the septum. Thickness rather 

 less than half the diameter. The sides are rather conical than even. Mouth 

 above half the diameter of the shell, long, narrowest toward the back, siphuncle 

 oval. Septa very numerous, not recurved towards the umbilicus." In the 

 British Museum with Sowerby's shells, numbered 44117a. It is stated to have 

 come from the Lias of Keynsham, but this is not the case. Mr. Crick has 

 shown (I. c.) that no such fossil is known to the collectors of that district, and 

 that the matrix resembles that of the Cornbrash and contains several fossils 

 which are characteristic, at all events, by their association, of that horizon. 



Description. — Specimens of this species occur of various sizes, some being 

 very large. As an example of the large form assumed, we may take the specimen 

 figured in PI. II, fig. 1. This has a diameter of 350 mm. ; the last half is body 

 whorl, and the rest contains 17 chambers, the last two being narrower. The 

 rate of increase, both as to diameter and thickness, is in the ratio of 7G : 100 

 per whorl. Its greatest thickness is at about ^ the way in between the periphery 

 and the umbilical edge. Beyond this point there is little convexity, but within 

 it has a convex slope towards the centre, thus forming a depressed umbilicus, 



