Manchester Memoirs^ Vol. Ixiii {i<^\()), No. 3. 3 



Measurments : — I. II. 



(Wild, VV669) (Marsden, L2827) 



Greatest Diameter ... ... 35 ... 74*5 mm. 



Height of outer whorl ... 15 ... 25*5 



Thickness of outer whorl ... 18 '5 ... 36 (ca.) 



Width of umbilicus (at margin) 13 ... 36 



Do. do. (at suture) 12 ... 29*5 



Greatest width of periphery ... i4"5 ... 26 (ca.) 



REMARKS. — The present species is founded upon the specimen 

 figured by Wild {ioc. fit), and a larger and more adult example from 

 the Pendleside Series of Marsden, Yorkshire. 



Wild's specimen, 35 mm. in diameter, consists of about one and 

 a half whorls, entirely septate, and terminating anteriorly with a septal 

 surface ; the external layer of the test has been entirely replaced by iron 

 pyrites, leaving the thick internal layer in the form of calcite ; the 

 surface of the casts of the septal chambers (camerse) is densely covered 

 with minute punct^e. This specimen shows the position of the siphuncle 

 in an excellent manner, owing to the weathering of the shell. 



The Marsden specimen is 74^5 mm. in maximum diameter and 

 possesses about three whorls ; it is somewhat crushed in places and 

 almost the whole of one side is missing. One portion of the periphery 

 shows several of the suture lines. Judging from the rounding off of the 

 umbilico-lateral angle on the last whorl, and the crowding together 

 of the lines of growth, the shell has evidently reached the adult stage 

 of growth. On the greater part of the specimen the test is well 

 preserved and exhibits the surface-markings in a perfect manner. This 

 specimen illustrates the later life-history of the species, as Wild's 

 example exactly fits the umbilicus. 



Affinities and comparison with other species. — Compared with 

 Phillip's type-specimen of Nautilus subsulcatus the present species is 

 a more rapidly increasing and relatively broader shell, having its 

 umbilical zone more nearly perpendicular to the mesal plane, and its 

 siphuncle nearer the ventral surface.* Its nearest ally appears to be 

 Ca'lonautilus quadratus, J. Fleming sp.,t a somewhat variable species 

 from the Lower Limestone Group of the Carboniferous Series of 



* The dimensions of Phillip's type-specimen, which is entirely septate and for 

 the most part an internal cast, are : — greatest diameter of shell, 66 "5 mm. (100) ; 

 height of outer whorl, 27 mm. (40) ; thickness of outer whorl, 25 mm. (37) ; width 

 of umbilicus (at margin), 30'5 mm. (46) ; ditto (at suture of shell), 23 5 mm. (35) ; 

 greatest width of periphery, 19 mm. (28) ; whilst at the diameter of Mr. \\ ild's 

 specimen, viz., 35 mm. (100), its measurements are : — height of outer whorl, 14 mm. 

 (40) ; thickness of outer whorl. 14 mm. (40) ; width of umbilicus (at margin), 19 mm. 

 (54); ditto (at suture of shell), 14 mm. (40); width of periphery, 11 mm. (31) 

 (Jide Crick). 



t J- Fleming, Hist. Brit. Anim. , 1828, p. 231. See also A. H. Foord, Cat. 

 Foss. Ceph. British Museum, part 2, 1891, p. 122. 



