NATTIUD^. 
141 
TEIASSIC SPECIES. 
Pleuronautilus distinctus, Mojsisovics. 
1882. Pleuronautilus distinctus. MojsisoTics, Die CepPalopoden der 
Mediterranen Triasprovinz (AbhdL der k.-k. geol. Eeiclisanst. 
Band x.), p. 278, Taf. Ixxxt. S. 4«, 46. 
S_p. Char. Shell planorbiform, consisting of about three very 
slightly embracing whorls, quadrangular in section, the periphery 
a little broader than the dorsal side. Umbilicus shallow, very 
wide, being a little less than haK the diameter of the shell. Septa 
rather numerous, about twenty-two may be counted in the last 
whorl of a specimen having a diameter of 2| inches ; they are 
moderately concave and form a shallow sinus upon the periphery. 
An internal lobe is present. The cast is marked upon the sides 
with a series of strong ribs (one to each chamber), which are 
coarsely tubercular uj^on the edge of the periphery, and fade off at 
the borders of the umbilicus. Siphuncle situated below the centre. 
Test imknown. 
liemarhs. The present species is distinguished from the nearly 
related P. semicostatus by the quadrangular form of its whorls, 
more rapid rate of increase, and the stronger ribs upon the outer 
whorl. 
Honzon. Trias (zone of Ceratites trinodosus). 
Locality. Schreyer Alpe, Gosauthal, near HaUstadt, Upper 
Austria. 
Kepresented in the Collection by a single example. 
Pleuronautilus subgemmatus, Afojsisovics. 
1882. Pleuronautilus suhgemmatus, Mojsisovics, Die Cephalopoden der 
Mediterraneii Triasprovinz (Abanhdl. der k.-k. geol. Reichsanst. 
Bandx.), p. 277, Taf. Ivxxv. tf. 2a, 2b. 
Char. Shell thick, discoid, whorls increasing rapidly in 
height and thickness, periphery smooth, the lines of growth and 
fine longitudinal lines crossing them being barely visible under a 
lens. The sides of the shell, on the contrary, exhibit about five 
longitudinal ridges crossed by fine lines of growth which impart a 
granulated appearance to the former at the point of intersection. 
Periphery broad, sui’face shghtly rounded, sides somewhat flattened, 
edges of the umbilicus sharply angular ; umbilical wall smooth, deep, 
falling obliquely down to the line of junction of the preceding whorl. 
The involution follows the line of the outermost of the longitudinal 
