268 
ERIK A : SON STENSIO 
The new genus from Tesssin, Meridensia, established by me in 1916 (Andersson 1916 a, 
pp. 25—29) also shows a number of primitive Palaeoniscid-like features with regard to 
the head skeleton. 
The sensory canals of the head. In Colobodus maximus and C. bassanii I was 
able to trace the sensory canals of the head practically throughout their extension. In 
C. konigi, on the other hand, I have only found them preserved in the ethmoidal region. 
As is seen in text figs. 85, 86 and 87, they run in the same way as in Perleidus 
woodwardi and Palaeoniscids. 
Fin skeleton. — While all the genera and especially Catopterus, Dictyopyge, 
Colobodus s. str. and Perleidus thus seem to show rather similar conditions with regard 
to the skeleton of the head, the same thing cannot be said about most of their fins. 
All the genera are, however, characterized 
by the abbreviate-heterocercal caudal fin. 
Catopterus and Dictyopyge have all the lepido- 
trichia of the anal and dorsal fins close 
together and jointed to the base, as is the 
case in Palaeoniscids and Platysomids. In 
Dictyopyge it is certain, at least as far as 
the anal fin is concerned, that the lepidotrichia 
and the endoskeletal radials corresponded 
to each other in number, indicating a fin 
musculature specialized in the direction of 
the higher Ganoids and Teleosts (cf. Schmal- 
haussen 1912, igi 3 a, igi 3 b). Little is known 
about the ventral fin. To judge from 
Dictyopyge rnacrura its lepidotrichia ought 
on the whole to be jointed. 
The unpaired fins show an essentially 
different type in Perleidus (de Allesandri 
1910, PI. II, fig. 2). The lepidotrichia of the dorsal and anal fins of this genus are not situated 
so close together as in the Palaeoniscids and are unjointed and unramified for a long distance 
proximally. The number of the endoskeletal radials is, at least in the dorsal fin, the same 
as that of the lepidotrichia. Both the exoand endoskeleton thus show in this case complete 
agreement with the higher Ganoids and Teleosts. The lepidotrichia of the ventral fins are, 
as in these forms, unjointed and unramified for a long distance proximally. Dollopterus and 
Meridensia resemble Perleidus at least with regard to the exoskeleton of their fins. 
In Colobodus x ) the lepidotrichia in the dorsal and anal fins are situated rather close 
together and the vast majority of them are also densely jointed. It is easy, however, 
to observe that a rather short proximal part is unjointed, that one or more joints 
immediately distally of this part are often longer than those following still more distally, 
or else that instead of the proximal unjointed part there are two or more strikingly long 
joints. It is also often possible to trace a tendency for the joints to fuse with one another 
J ) Observations made on specimens belonging to the Palaeontological Institute of Upsala. 
Text fig. 85. Colobodus bassa. 
After a specimen belonging to the 
at Upsala P . 7 25 . »/ 4 . Sensory can 
Mx , maxillary; Op , operculum ; Po , p 
