Bashford Dean 219 
Lebach) in the Berlin Museum, for the inspection of which I am greatly 
indebted to Professor Jaekel. For they show not only the lateral line 
but its many branches, the sensory canals of the head, and, most inter- 
esting of all, the auditory organs and the rim of the nasal capsule. Thus, 
in the specimen shown in Fig. 28, one readily distinguishes ~ the canals 
of right and left sides, //, J, from which a series of vertical branches arise 
very much as in recent selachians, cf. especially in the young specimens 
(20-30 cm.) of Chlamydoselachus; the lateral lines apparently draw to- 
gether in the occiput and from this region pass forward, giving off 
various branches, a supraorbital canal, swpra o; there, also, appear a 
suborbital canal, swb o, an auditory capsule, au, of extraordinary size, 
and traces of sensory canals, br s, in the branchial region, again a condi- 
tion which suggests the modern shark (Chlamydoselachus). These con- 
ditions are shown to even better advantage in a specimen from the same 
collection shown in Fig. 29. Especially noteworthy are here: (I) The 
position of the suborbital canal, for it is seen to arise (contrast Reis’s 
note given above) from the main canal passing to the trunk, 7. e., in the 
position usual in fishes. (II) The great size of the sensory branches 
passing to the region of the gills. (IIL) The structures of the auditory 
organ, the utriculus, wtr, and, prominently shown, a vertical simicircular 
canal, vse. (IV) The upper margin of the nasal capsule, nas, which indi- 
cates accurately the position of this organ. 
In the manner of the protection of the lateral line the Acanthodians 
show a range of evolutional characters; in Huthacanthus elegans the canal 
is marked only by a ridge-like prominence of marginal scales (Figs. 34 
and 34a) ; in Acanthodes bronni the marginal scales become enlarged and 
prosalient (Fig. 35) ; in Huthacanthus gracilis they may completely over- 
lap and enclose the sensory canal (Fig. 33). It is finally observed that 
a great range in the manner of protecting the sensory structures is found 
at different regions in the same individual. 
Relationship of the Acanthodians.—It has been pointed out in the 
foregoing notes that the Acanthodians agree in a number of regards with 
the Cladoselachian sharks, and that from this evidence we conclude that 
they are more closely related to these forms than has hitherto been gen- 
erally accepted. Dental characters, structures of fins caudal, unpaired 
and paired, vertebral axis, even the mode of protection of the eye, are 
In A. bronni the shagreen denticles are reduced in size; those only are 
large which protect the sensory canals, hence the clearness with which the 
arrangement of the canals may be followed. 
