Pisces. ] UPPER PALZOZOIC VERTEBRATA. 615 
middle of body the oblong scales are three times deeper than long, their proportional length being about *, 
(or one-tenth of the greatest depth of the fish at that region) : domed the ventral margin at ae of anal 
fin the scales are much smaller and more nearly square ; they are acutely rhombic, and longer than deep on the 
pedicle of the tail; about three of the anterior anal or dorsal fin-rays in a space equal to the width of one 
of the oblong scales on the middle of the body; fulcral scales on upper edge of tail strongly developed ; bones 
of the head finely marked with vermicular ridges and granules, and in parts striated like the scales ; articulating 
claw of scales ver Al large, and articular ridge strongly marked, rounded. 
This species is most nearly allied to the P. macrurus, from which it differs in the more obtuse angulation 
of the profile of the occipital crest, and the consequently greater slope both of the back and line of the face, 
it also differs in the smaller size of the tail, and very obviously in the anal and dorsal fins extending much 
nearer to the head, and being narrower, wanting the large, broad, faleate anterior expansion of that species, &e. 
Prof. King has examined the original specimen, figured by Mr Winch, in the Transactions of the Geological 
Society of London, (Vol. IV. t. 2), on which figure M. Agassiz founded his P. parvus; he finds that the 
published figure is very inaccurate, and that the specimen is certainly the young of P. striatus. The head is 
very slightly larger than that of the P. gibbosus, to which it is probable the species should be united, as I do 
not find the difference of inclination of the spinous processes alluded to by Agassiz to exist. The articulations 
of the dorsal and anal fins are said by Agassiz to be twice as long as wide, but in reality only a few at the 
base have this proportion, the succeeding and more numerous ones haying the length and breadth about equal, 
and by far the largest number being considerably wider than long (at least double). 
Position and Locality—Rare in the Permian marl-slate of East Thickley. 
5th Order. Puacoipa. See page 575. 
The following species of fish are universally referred to the tribe of Plagiostomous fishes, (see page 576,) 
and most of them I have no doubt are rightly so referred; but some of them I think may reasonably be 
suspected of belonging to other groups, and most of the disjoined portions known present characters of such 
obscure systematic relation, that I think it better not to attempt to group them into families, nor to adopt the 
groupings which have been published, which I think separate forms which probably belonged to different parts 
of one fish, and connect forms which have no intimate relations. In the present state of knowledge of these 
fragmentary genera, therefore, I prefer giving them simply in alphabetical order. I have taken great trouble 
to ascertain what genera and species were intended by the MSS. names of the lists in Agassiz’ Poissons 
Fossiles, Vol. I11., so as to give him credit for them as if they had really been described or figured, which 
however is here done for many of those species for the first time. 
Genus. ASTEROPTYCHIUS (4g. name only). 
Gen. Char.—Bony fin-ray compressed, long, slender, gradually tapering to a point at the distal end, and 
abruptly tapering at the striated proximate end, or base of insertion; sides moderately convex, converging to 
the anterior edge, which is strongly keeled; posterior face with a moderate cavity, each lateral edge having a row 
of small pointed teeth, directed upwards. Surface of the sides with several smooth, thread-like ridges, separated 
by broader, flat, longitudinally striated spaces, on which are irregularly scattered, smooth, spinous tubercles. 
The posterior teeth being directed upwards, and the tubercles set between the longitudinal ridges of the 
surface, separate these species from Leptacanthus. 
They are only known at present in the carboniferous rocks. 
ASTEROPTYCHIUS ORNATUS (Ag. name only). Pl. 3. K. fig. 23, 24. 
Desc.—Average length about four inches; greatest width at base three and half lines, tapering upwards 
at the rate of one line in one inch; sides with three (or rarely four when about three lines wide) narrow, 
smooth, longitudinal ridges, exclusive of the anterior keel; between each pair of ridges is a wider flat space, 
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