XAUTILIDJS. 
307 
greater diameter of the shell 0*72 inch. Some imperfect adult 
individuals before me, too much broken to afford exact measure- 
ments, were evidently as much as three times the linear dimensions 
of that from which the foregoing dimensions were taken. 
“ This common species has been wrongly identified with several 
foreign forms. D’Orbigny, in his ‘ Prodr. de Paleont.’ \ expresses 
the opinion that his own Icevigatus^ published in 1846 ^ (not his 
N. IcBvigatus^ 1840), is synonymous with it ; also the Indian N, 
sphcericus and X. Orhignyanus, Forbes^, and a Chilian form referred 
by Professor Forbes to N. Icevigatas. Mr. Blanford however, 
considers both of the Indian shells merely varieties of N, Bouch- 
ardiamis, d’Orbigny, and entirely distinct from N. Dekayi, Morton. 
I have not the necessary specimens at hand to express any decided 
opinion in regard to the Indian shells figured by Mr. Blanford all 
belonging to the one species X. Bouchardianus ; but I can fully 
concur with him in the opinion that they are certainly distinct from 
X. Delcayi^ Morton. The latter differs, as stated by Mr. Blanford, 
in having its umbilicus always filled with a solid shelly kind of 
columella, formed by the thickening of the lip at its connection 
with the body of the shell on each side, instead of being perforated. 
X. Dekayi also has its aperture constantly more transverse, and its 
siphuncle always nearer the inner side, as may be seen by our 
figure 1 rt, plate 27, which represents very nearly the typical form 
of the species, as I know from a direct comparison with Dr. Morton's 
type specimen, now in the Museum of the Academy of Natural 
Sciences at Philadelphia ; . . . . 
“ It is true that Dr. iMorton also referred doubtfully to X. Dekayi^ 
1 Vol. ii. 1850, p. 211. 
^ “ His figures of this shell given in the ‘Voyage of the Astrolabe’ agree 
very closely in form, as well as in the outline of the aperture and the position 
of the siphuncle, with N. Dekayi ; but as they were drawn from an internal 
cast only, we have not the means of knowing certainly whether or not the 
small umbilical perforation seen in the cast was entirely filled with a solid eolu- 
melladike callosity on each side, as in Morton’s species. If it has this 
character, it may be identical with that form.” {Meek.) 
® Trans. Geol. Soc. ser. ii. vol. vii. pt. iii. Report on the Fossil Invertebrata 
from Southern India, collected by Mr. Kaye and Mr. Cunliffe, pp. 97, 98. 
l(8vigatus and X. sj^hcericus. 
Meek is here in error ; the Chilian form is N. d' Orhignyamis, not N. Icevi 
gatus, which is from Southern India. N. d' Orhignyanns, Forbes, is described 
and figured in Darwin’s ‘ Geological Observations,’ 1846, pt. hi., Appendix, 
p. 265, pi. V. If. 1 n, 1 h. (Parts i. and ii. of this work were published 1842 
and 1844 respectively. The main title bears date 1851.) 
^ Mem. Geol. Surv. of India — Palaeont. Indica — i. Cretaceous Cephalopoda 
of Southern India, 1861, p. 15. 
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