Permian Fish Menaspis. — Dean. 53 
their rounded bases, as is well shown in the type specimen, 
they were evidently movable . In point of size, moreover, thev 
best correspond to the elements referred to in Sqnaloraja. 
Such structures would, moreover, be apt to take a position 
dorsal to the antero-ventro-lateral head spines during- the pro- 
cess of fossilization . 
The above considerations lead us, accordingly, to infer 
that Menaspis, although showing a number of shark-like fea- 
tures, was an early chimaeroid. Its likeness to chimseroid 
rather than to shark is shown notably in the dentition, in the 
character and disposition of the lateral head spines, and in the 
remarkable paired "spines" which may be compared to the 
"labial" structures of Squalorajid. Conclusive proof of its 
chima?roid affinities, however, will be lacking until it can be 
shown that the erectile frontal spine was present in the male 
(the type specimen may have been a female), and that it pos- 
sessed a dorsal fin-spine and the peculiar vertebral-column 
known to have been possessed by chimaeroids from mesozoic 
times. The evidence for the present interpretation of Men- 
aspis is at least adequate, I conclude, to enable us to inter- 
pret the most troublesome features of the fossil. It is no 
longer a nebulous "trachyacanthid" with vague affinities to 
doubtful early groups, but instead, a form well proportioned, 
(Cf. Figs. I A and B), after the fashion of shark or chimce- 
roid, but with its major features allying it with the latter 
group. It is remarkable. in the possession of well-marked lat 
eral head spines, and in a series of three pairs of greatly elon- 
gated and curiously unsegmented spine-shaped cartilages. In 
the former regard, agreeing with older chimseroids, it presents 
more specialized dermal developments than are known to have 
been developed in the contemporary sharks. In the latter re- 
gard it is certainly extraordinary, although, as above noted, 
somewhat similar structures exist in Sqnaloraja. In short, 
we reasonably conclude that in Menaspis there is preserved 
a Permian chimseroid representing a distinct family ( Men- 
aspidse A. S. W.) provisionally to be placed near the INIyria- 
canthidce and Squal(irajida\ The larger question of the re- 
lationships of the chimxroids need hardly enter into the pres- 
ent discussion . It may be enough to indicate that in the mat- 
ters of dermal defenses and teeth the Permian chimaeroids re- 
semble the contemporary cestraciont sharks. 
