CLASSIFICATION OF DEVONIAN FISHES 423 
while the interval left between them and the mandibular rami, on 
each side, is taken up by a series of smaller, quadrate plates, which 
increase in size from before backwards—the /ateral jugular plates (J?) 
There is no rhomboidal median jugular plate interposed between the 
anterior part of the inner edges of the principal jugular plates. The 
teeth are of two kinds ; smaller, set in a close series along the edges 
of the jaws; and larger, placed at intervals along the palate, and 
perhaps along the inner side of the mandible. The larger teeth 
have grooved bases, and appear to be composed of dendrodentine.! 
The pectoral arch is covered by two triangular, sculptured, osseous 
plates (Pct+, Pct*), which meet in the middle line below and are 
superficial to the so-called coracoids. The paired, or pectoral and 
ventral, fins are lobate ; that is, the fin has a central axis, or stem, 
covered with scales. There are two dorsal fins, placed in the pos- 
terior half of the body. The ventral fins are situated under the first 
dorsal, and are succeeded by a single anal. The caudal fin, whose 
contour is rhomboidal, is divided into two eaual lobes by the pro- 
longed conical termination of the body ; in other words, the fish is 
diphycercal, or truly homocercal.? 
Every ichthyologist will admit the singularity of this combination 
of characters, but a careful analysis of the structural peculiarities 
presented by other fossil fishes of the same age, will show, that, so 
far from isolating Glyptolemus, they closely unite it with several 
other genera. 
That genus which appears to me to approach it most closely is 
the Gyroptychius of M‘Coy, whose structure has received admirable 
elucidation from Professor Pander in his beautiful monograph 
“Ueber die Saurodipterinen, Dendrodonten, Glyptolepiden und 
Cheirolepiden des Devonischen Systems” (1860), to which I may 
refer those who desire to obtain a more particular acquaintance 
with the details of its organization. 
Here I must content myself with reproducing in a reduced wood- 
cut (fig. 3) Professor Pander’s restoration of the fish, which may 
be compared with the restored woodcut of Glyptolemus (fig. 1) 
1 Prof. Pander applies the term ‘‘ Dendrodonts” to those fishes the pulp cavities or whose 
teeth appear branched, in consequence of the folding of their walls ; and such folded dentine 
may be conveniently termed ‘‘ dendrodentine.” 
2 I have endeavoured to show elsewhere (Quarterly Journal of Microscopical Science, Oct. 
1858) that the so-called ‘‘homocercal” Tedeoste? of the present epoch are in reality 
excessively heterocercal ; but the word ‘‘homocercal” is now so generally understood to 
signify a tail like that of most existing 7edeosted, that I prefer to employ Prof. M‘Coy’s term 
“ diphycercal” for truly homocercal tails. See, on this point, Kélliker, ‘‘ Ueber das Ende 
der Wirbelsdule der Ganoiden, 1860,” and Van Beneden, ‘‘ Sur le Developpement de la Queue 
des Poissons Plagiostomes,” Bull. de Acad. Royale Belgique, 1861. 
