XAUTILTD^. 
187 
Sp. Char. Shell moderately inflated, rapidly tapering; section of 
whorls nearly circular ; septa rather deeply concave ; sutures with 
a conspicuous inner lobe. Siphuncle a httle above the centre in the 
very young shell, but becoming central in the more advanced stages of 
growth. Surface of the test marked only with fine lines of growth. 
RemarTcs. This is a very badly characterized species, owing to the 
imperfect condition in which it is found, fragments only being 
known. The specimen figured by Munster (Joe. cit.) is only 7 lines 
in length, that figured by Laube only 5|, but Mojsisovics figures in 
the ‘ Ceph. d. Mediterr. Triasprov.’ a large fragment, nearly 3 inches 
in diameter. It seems very questionable whether this belongs to 
Munster’s tiny species, especially as Mojsisovics considers that his 
specimen is related to Nautilus Caroliniis, Mojs., and N. suhcaroliuus., 
Mojs., both of which are very considerably larger than N. linearis. 
The present species is said to be rare. 
Horizon. Upper Trias ; Cassiauer Schichten (St. Cassian Beds). 
Locality. St. Cassian, South Tyrol. 
liepresented in the Collection by a few fragments. 
Nautilus (Clydonautilus) spirolobus, Dittmar. 
186G. Nautilus spirolohus, Dittmar, Zur Fauna der Hallstadter Kalke 
(in geognost.-paliiontol. Beitrage, Band i. Heft ii. b), p. (34) 352, 
Tab. xiii. ff. 1, 2. 
1869. Nautilus Goniatites (Hauer), Mojsisovics, Gliederung der oheren 
Triashildungen, Jahrh. Geol. B. A. p. 95. 
1873. Nautilus spirolobus, Mojsisovics, Das Gehirge um Hallstatt 
(Ahhandl. der k.-k. geol. lieichsanst. Band vi.), p. 28. 
Sp. Char. Shell Nautilus-like, involute, inflated, rapidly increasing 
in height and thickness. Umbilicus closed. Greatest thickness, 
which exceeds the height, at the umbilicus. The septa are some- 
what numerous, the sutures are much bent upon the sides of the 
shell, forming a deep and wide lateral backwardly directed lobe, 
and a smaller one (directed forwards) in the umbilical region. Again, 
on the periphery there is a deep and narrow backwardly directed 
lobe. 
The test is covered with fine but distinct transverse raised lines 
or ridges, which form a slight sinus in the median line of the 
periphery, showing the shape of the emargination of the aperture. 
A peculiar feature in this species is that each suture touches the 
preceding one at a point near the border of the periphery, the sides 
of the lobes thus joined having the appearance of a continuous line 
running longitudinally on each side of the peripheral lobe. This 
feature is common to all stages of growth. 
