COILOPOCERATID®. 89 
similar to those of Cotlopoceras but are still more like those Styracoceras 
balduri. The siphonal saddles are small and bifid in these two genera. 
The small first lateral lobes may be reckoned either as mere marginals in 
this genus dividing the first lateral saddles equally or as true first laterals. 
The two small saddles coming next to these resemble the corresponding 
saddles in Coilopoceras. Uhlig in his Die Cephalopodenfauna der Teschener 
und Grodischter Schichten® figures several species mentioned below, one of 
which has a rounded venter with the usual smooth sides and characteristic 
sutures of this genus. Uhlig takes the same position that has been here 
independently assumed, namely, that the sutures are similar to those of Styr. 
balduri (Keyserling), and that the affinity of this genus for Mojsisovicsia 
is shown by the development of one of his species which has a rounded 
venter until a late stage. The sutures and the affinities of this fossil for 
P. heteropleurum show that this is a prolonged, immature, or arrested condi- 
tion of ontogenic development, and therefore an indication of remote rather 
than proximate derivation from Mojsisovicsia, whose sutures are widely 
different. The section of P. heteropleurum given hy Struckmann”’ shows that 
the transition from a rounded to an acute venter probably takes place 
directly at a comparatively early stage, as might be imagined after study 
ing the ontogeny of P. pseudograsianum. This fact shows that the resem- 
blanees of the sutures with those of Styracoceras have no genetic significance 
because the extraordinary and complex ontogeny of that genus indicates 
very distinct affinities. 
PLATYLENTICERAS HETEROPLEURUM (Neumayr and Uhlig). 
Oxynoticeras heteropleurum Neamayr and Uhlig, 1881, Paleontogr., Vol. X XVII, 
pl. 15, figs. 1, 2. 
This species has smooth compressed volutions but the involution is not 
sufficient to cover the sides and the umbilici are quite large. The keel is 
acute and so far as can be seen in the figures is apparently solid. The 
sutures as drawn by the authors cited are not at all like those of true Oxyno- 
ticeras, which have only one first lateral saddle, but are similar to those of 
Styracoceras balduri, as stated above. It is not practicable to determine 
@Denksch. K. Akad. Wiss., Wien, Vol. LX XII, 1901. 
b Jahrb. K. preuss. geol. Landesanstalt, 1889, p. 71, pl. 11. 
