552 G. C. Cricli — On Vestinautilus. 



action of air and water, and of insects and otlier organisms gaining 

 access to it through the interstices of the breccia, would soon 

 disappear. 



With the limited time and opportunities which I had, I was not 

 able to form an exact idea of the extent of the formation. Its width 

 is that of the slope to which I have referred — from two to three 

 miles, perhaps more in places. The thickness must vary from point 

 to point ; it may sometimes — with interstratified beds of sand — 

 amount to as much as five or six hundred feet. The length near 

 Tumupasa will be equal to that of the Bala-Susi mountains, nearly 

 a hundred miles, but breccias must be forming under exactly similar 

 conditions in many other places at the foot of the outer ranges of 

 the Eastern Andes. 



It is sufficient for the present if I have shown that extensive 

 breccia formations, in many respects similar to those found among 

 the European strata, are now being accumulated in a thickly wooded, 

 well-watered country, with a moderately warm and nearly uniform 

 climate. 



IX. — Note on Vestinautilus crassimarginatus, A. H. Foord. 



By G. C. Crick, Assoc.E.S.M., F.G.S., of the British Museum (Natural History). 



rpHE species Vestinautilus crassimarginatm was founded in 1900 

 X by Dr. A. H. Foord ^ upon some (apparently three) spec mens 

 from the Carboniferous Limestone of Little Island, near Cork. It 

 was described as follows : — 



" Shell discoid, with slowly increasing whorls, all exposed in 

 a deep umbilical cavity having a large central vacuity. The whorls 

 are digonous in section, the peripheral area making a broad flattish 

 arch; the sides, which form the steeply descending umbilicus, 

 diverge at an obtuse angle from the margin of the latter ; they are 

 somewhat inflated in the lower half, and slightly concave in the 

 upper, resembling those of Vest. cariniferus~ in this respect. The 

 contact or inclusion of the whorls is very slight, and, so far as can 

 be made out from a section, there is no perceptible zone of 

 impression. Owing to this slight amount of overlapping of the 

 whorls, part of the peripheral area is exposed in the umbilicus, the 

 inner whorls thus making a deep channel where they abut against 

 those that embrace them. The umbilical border is marked by 

 a strong, rounded rim, which becomes very prominent in the adult 

 and senile stages. 



"In the young shell the rim is about as prominent as it is in the 

 adult of Vest, cnriniferus, J. de C. Sow. [sp.], and other allied 

 species. The conical apex of the young shell is ornamented with 

 a series of close-set, fine, longitudinal ridges, and these ai'e crossed 



1 Monoo-raph on the Carboniferous Cephalopoda of Ireland (Pal. Soc), pt. iii 

 (1900), p.^O, pi. xxiii, figs. 5a-c. 



^ Nautilus cariniferus, J. de C. Sowerhy, Min. Con., vol. v, p. 130 (1824), 

 pi. cccclxxxii, fig. 3, excl. fig. 4. See also A. H. Foord, Mon. Carb. Ceph. Ireland 

 (Pal. Soc), pt. iii (1900), p. 82, pi. xxiii, figs. 1-3 ; pi. xxvii, figs. 2a, b. 



