Cope. | 578 [March 7, 
In 1871* the writer gave the following as the primary divisions of the sub- 
class Pisces: Holocephali, Selachi, Dipnoi, Crossopterygia, Actinopteri. 
The Holocephali was raised to an equivalency with the other sub-classes 
on account of the absence of distinct hyomandibular bone. The Dipnoi 
were defined by the median pelvic element, by the distichous arrangement 
of the segments of the pectoral and ventral fins, when present, on a me- 
dian axis, and by the supposed presence of a distinct hyomandibular bone. 
The latter definition must be abandoned, for though an ossification exists, 
it has been shown by Stannius, Huxley and Giinther, to be merely a de- 
posit in the continuous chondrocranium. The sub-class Crossopterygia 
was substituted for the sub-class Ganoidea of Agassiz and Miiller, as the 
latter was believed to have no actual existence as a division of fishes, After 
comparing the osteology of Polypterus, Lepidosteus and Amia, I remark 
(p. 820) ‘It is thus evident that the sub-class Ganoidea cannot be main- 
tained, It cannot be even regarded as an order, since I will show that 
Lepidosteus, Accipenser, and Amia, areall representatives of distinct orders. 
Thope, also, to make it evident that Polypterus should be elevated to the 
rank of a sub-class or division of equal rank with the rest of the fishes and 
with the Dipnoi, already adopted.’’ The sub-class Ganoidea has not yet 
fallen into disuse, but there are strong symptoms that it will do so.+ 
Among others I select the following extract from Huxley’s paper on the 
ovaries of the smelt, published in 1883. + 
“As is well known, Lepidosteus presents an example of a Ganoid with 
oviducts like those of the higher Teleostei; in Osmerus, on the other 
hand, we have a Teleostean with oviducts like those of the ordinary 
Ganoidei. It is tolerably obvious, therefore, that the characters of the 
female reproductive organs can lend no support to any attempt to draw 
a sharp line of demarkation between the Ganoids and the Teleos- 
teans, 
‘Boas has recently conclusively shown that the same is true of the sup- 
posed distinctive character afforded by the conus arteriosus; and it has 
long been admitted that the spiral valve which has been described in the 
intestine of Chirocentrus is the homologue of that which exists in all the 
Ganoids, though greatly reduced in Lepidosteus. Indeed I am inclined to 
believe that the circular valve which separates the colon from the rectum 
in the smelt is merely a last remainder of the spiral valve. Thus, among 
the supposed absolute distinctions between the Ganoids and the Teleostei, 
only the peculiarities of the brain, and especially the so-called chiasma of 
the optic nerves, remain for consideration. My lamented friend Mr. 
Balfour, in the last of his many valuable labors, proved conclusively that 
the brain of Lepidosteus is, both in structure and development, a 'Teleostean 
* Proceedings Amer, Assoc, Adv, Science, p. 826. Transac. Amer, Philosoph. 
Soc., p. 449, 
+The term ganoid can be used as an adjective to describe the scales already 
known by that name, and thus be preserved, 
{ Proceedings Zoélogical Society of London, 1883, pp. 187, 188, 139, 
