STJPPLEMEN^T. 
393 
greatest diameter of the shell. Septa numerous, moderately concave ; 
sutures forming a shallow, hackwardly-directed sinus on the sides of 
the shell, then inclining forwards and passing over the periphery 
with a slight median sinus. Siphuncle not observed. The flattened 
sides of the whorls are ornamented with transverse ribs radiating 
from the umbilicus, and abruptly terminating at the subangular 
edge of the periphery. The ribs are crossed by three rows of 
prominent, elongated nodes, those on the edge of the periphery 
being the largest. The periphery of the adult shell is broadly and 
evenly rounded, but that of younger shells exhibits a slight depres- 
sion in the median line, caused by the pressure of the succeeding 
whorls. This depression is not shown in Mojsisovics’s figure, which 
represents a much larger shell than the one in the British Museum, 
from which the present description is, in the main, drawn up. The 
whole of the test is covered with fine subregular lines of growth, 
which form a deep, hackwardly-directed sinus in passing over the 
periphery. The lines of growth are crossed by fine thread-like 
lines, the two series, seen under a lens, exhibiting a beautifully 
cancellated appearance. 
Ilemarhs. This species is nearly related to Pleuronautilus 3Iosis, 
Mojs. (see supra, p. 135, fig. 22), hut differs from it in possessing 
three rows of nodes upon the ribs, which latter are also much less 
numerous in P. trinoclosus than they are in P. Mosis. 
Horizon. Zone of Tracliyceras Aonoides (beds with Lohites 
ellipticus) ; Karnische Stufe, Al^une Triash 
Locality. Feuerkogel, near Aussee, Tipper Austria. 
Eep resented in the Collection by a single example (No. C. 3431). 
Subgenus HERCOGLOSSA. 
[See supra, p. 180.] 
Nautilus (Hercoglossa) Sauperi, Mojsisovics. 
[See supra, p. 185.] 
Several specimens of this species having been added to the 
Collection, I take this opportunity of amending the description 
given on p. 185 of the present volume, as respects the sutures. The 
form of the latter is not clearly shown in Mojsisovics’s figures, 
^ See Mojsisovics, “ Ueber die Gliederung der oberea Triasbildungen der 
ostlichen Alpen,” Jahrb. der k.-k. geol. Reicbsanst. 1869, Band. xix. p. 91 ; also 
Credner, ‘Elemente der Geologic,’ 6th ed. 1887, table, p. 586. 
