On the Fossil Fishes of the Carboniferous Limestone Series of Great Britain. 403 
Genus—Lophodus, Rowanowsky. 
Lophodus—H. Rowanowsky, 1864. “ Bull. d. 1. Soc. Imp. des Nat. de Moscou,” p. 160. 
Helodus (partim)—A gassiz, and others. 
Teeth, generally much broader than long, median surface produced to form a 
conical summit ; root compressed and regularly striated. The surface of the crown 
is covered with enamel, finely punctate. The form is not ordinarily symmetrical ; 
occasionally, irregularly contorted. The anterior basal margin is produced and 
forms a sharp edge. The transverse section “exhibits the form of a nail with a 
conical head.” 
M. H. Rowanowsky describes the microscopical structure as being very uniform 
in the different species, it is characterised by the union of the central medullary 
canals, relatively large and irregular, giving rise to a number of smaller canals, 
generally bifurcating, and radiating towards the surface where they are externally 
visible as minute pores; all the canals branch into a large number of minute and 
short, dentritic calciferous tubes. 
The genus Lophodus was created by M. Rowanowsky for the reception of teeth 
of fishes in which the crown of the tooth is more or less conical with a concavity 
of the base which corresponds to the convex surface of the crown. 
The root is deep but not thick. The teeth comprised in the genus Lophodus 
were described by Prof. L. Agassiz as Helodus, and other authors to the present 
time have followed, for the most part, his initiative. The species H. mammillaris 
and H. didymus of Agassiz are referred to the new genus, whilst /Z, planus and H. 
turgidus, Agass., are considered as the types of the old genus Helodus. 
It is questionable to what extent the re-distribution of M. Rowanowsky may 
prove correct. Helodus planus was considered by the late Prof. Agassiz, and is 
now generally accepted as belonging to the same fish as Psephodus magnus. 
And the somewhat miscellaneous group of Helodus turgidus has since been revised 
and amended. There is also the important discovery described by Messrs. Newberry 
and Worthen, (“Palzeont, Illinois,” Vol. II., p. 88.) of the teeth of Helodus and 
Cochliodus being found impacted together as to leave no doubt that they originally 
belonged to the same fish. Some of the teeth so found, as for example, the one repre- 
sented in pl. VL, fig. 4a, op. cit. bears a tolerably close resemblance to the typical 
species of Lophodus figured by M. Rowanowsky. On the other hand, if the genus 
be confined to teeth which have occupied a similar position and have been arranged 
in the same way as Orodus, or the recent Cestracion, there is every possibility that 
it may prove a good and satisfactory genus. 
Messrs. Newberry and Worthen instituted the same name in 1870 (‘Survey of 
Illinois,” Vol. IV., p. 360) to designate a genus of fossil fish which name has since 
been transformed by Messrs. St. John and Worthen into Agassizodus (“ Palzeont. 
Tlinois,” Vol. VI., p. 311). 
