88 University of California Publications in Zoology 
though the possibility exists that in some it may have been 
present, and have been torn off in dissection. Polyodon has a 
very deeply pigmented pial covering of the brain, but it remains 
thin and membranous over the fourth ventricle. I myself ex- 
posed several brains of Amia with the myelencephalie gland 
especially in mind and found no trace of such a gland there. 
This was unexpected, since Amia is without doubt the form 
nearest allied to Lepisosteus. 
In an article on the central nervous system of Protopterus 
annectens, only the preliminary report of which was accessible 
to me, Burekhardt (1892) figures the dorsum of this dipnoan 
brain with a structure possessing numerous diverticula lying 
over the hind-brain, which he ealls the “‘saceus endolymphat- 
icus.’’ This figure is reproduced by Wiedersheim (1909, fig. 
2014, p. 296). In a longitudinal section of the same brain (fig. 
2028 in Wiedersheim) this ‘‘saceus’’ has seemingly been re- 
moved, as the myelencephalon is covered only by the much folded 
choroid plexus. Whether or not Burckhardt’s ** 
saccus endolym- 
phaticus’’ of Protopterus is im any way related to the myelence- 
phahie gland in Lepisosteus, 1 am unable to say at the present 
time, but judging from the name and its appearance in the 
figure, it is highly improbable. If this should be found to be 
homologous, it is all the more strange that it does not appear 
in Ama. 
GENERAL MORPHOLOGY 
The general form of the gland in Lepisosteus osseus is not 
bilobed as described by Herrick (1891), but it is trilobed. 
The main body of the gland is slightly wider than long, and is 
thickened just cephalad of the middle, sloping off towards the 
front and back, and with a pronounced median sulcus caudally, 
causing the posterior border to be emarginate. From the antero- 
lateral angles there projects on either side an ear-like lobe, very 
definite and constant in shape and size, connected with the main 
body by a rather slender neck (fig. A). These ear-like projec- 
tions are entirely surrounded by cartilage, making their dis- 
section rather difficult, although they readily hold their shape 
and position when freed from the cartilage. 
