20 
and exhibits only concentric lines of growth. The infraclavicle (PI. IV, 
Fig. 3, icl.) is relatively large, tapering forwards to a blunt point. The 
pectoral fin (PI. IV, Fig. 2, pet.) is only known by fragments, but its rays 
seem to be similar to those of the other fins. The pelvic fin ( plv .) is better 
shown and remarkable for the length of its base-line; though its maximum 
depth probably almost equalled this length. It comprises at least twenty-five 
rays, which are only articulated at distant intervals, but very finely divided 
distally ; and in the anterior part of the fin in the type specimen there are 
traces of the row of stout supporting baseosts. The dorsal fin ( cl .) comprises 
about thirty rays, of which the few foremost gradually increase in length to 
the longest ; and the extreme height of the fin nearly equals the depth of the 
trunk at its insertion. The rays are distantly articulated, and supported by a 
less numerous series of short and stout baseosts, which are opposed to an 
equal number of longer axonosts, all very imperfectly calcified. The anal fin 
(an.) arises opposite the middle of the dorsal and is apparently similar to the 
latter. Some of its imperfectly calcified baseosts and axonosts are well shown 
in the type specimen, thirteen of these supports corresponding with about 
twenty-one rays. The upper caudal lobe is remarkably slender, and the caudal 
fm (c.) seems to have been only very slightly forked. Its stout distantly- 
articulated rays are finely divided distally. 
Squamation. — A patch of thin rhombic scales is always seen covering 
the lower part of the abdominal region. Some of the scales are slightly 
deeper than broad, while those near the ventral border are about equilateral ; 
and all exhibit marks of their concentric lines of growth. There are also 
thicker and smaller rhombic scales on the upper caudal lobe. No ordinary 
scales, however, are preserved on any other part of the fish ; and the only 
remains of dermal armature are a row of thick scutes along the lateral line of 
each side (PI. IV, Fig. 2, sc.). These scutes are <-shaped or arrow-head- 
shaped, and arranged in close series, partly overlapping, with the apex 
directed forwards. 
Family — PLATYSOMID-ffi. 
Genus — PLATYSOMUS, Agassiz, 1835. 
(Poiss. Foss., ii, Pt. i, pp. 6, 161.) 
Cbs. — This genus ranges from the Lower Carboniferous to the Upper 
Permian in Europe, and has also been discovered in the Coal Measures of 
North America, It is only represented in the collection from St. Peter’s by 
