TRIASSIC FISHES FROM SPITZBERGEN 
XIX 
under normal conditions of the fish horizon itself is shown in text fig. c, where we can 
see fragments of shale, limestone and croncretions on the slope. 
The occurrence and state of preservation of the fossils from this horizon were 
described by Wiman in 1914 (1914 b, pp. 8 —-10). 
With regard to the evertebrate fauna of the same horizon I have little to say, as 
the material of evertebrates brought home during the last few years has not been 
investigated. It is noteworthy, however, that Gyronites aplanatum White is very common. 
For the vertebrate fauna I may refer to my account in the next chapter. 
Middle Triassic.series. — In this work I have like Stolley provisionally reckoned 
the middle Triassic series from the upper boundary of the fish horizon, a view which. 
Text fig. c. Part of Mt Trident with Sticky Keep in the background. In the nearest foreground is the fish horizon, 
bounded above by the shaly cliff. In the portions of the mountain farther back the upper boundary of the fish horizon 
and the lower and upper Saurian horizons is marked. 
as we shall see, is supported also to some extent by the vertebrates. In order to decide 
with full certainty whether the boundary is to be drawn in this way we need, however, 
a more detailed knowledge of the evertebrate fauna than we have at present. 
In the middle Triassic series the rocks consist mainly of black or more or less 
bituminous shales that often easily split into thin laminae. Here and there limestone 
beds appear in the shales and these may contain phosphorite, especially up towards 
the upper Saurian horizon. Below the lower Saurian horizon there also appear in certain 
strata numerous large and rather flat concretions, often situated so close together that 
they form real banks (Mt Congress, Mt Tschermak, Mt Bertil), some of which are often 
rich in fossils. The fossils are chiefly Ichthyosaurians, which are always, however, in 
a bad condition because of frost weathering, so that scarcely anything but the vertebrae 
S ten si 6, Triassic Fishes from Spitzbergen. d 
