Permian Fish Mcnaspis. — Dean. 51 
to the head.* According to Jackel's interpretation, on the 
other hand, a large gap must have existed between the head 
and the pectoral region, and consequently, there was present, or 
might have been present, a greater number of gills in this 
form. One observes, furthermore, that in the present render- 
ing the ventral fin occurs in the position in which it usuallv 
occurs in shark-shaped fishes. In Jaekel's interpretation, on 
the contrary, they must have occupied a position far back on 
the trunk, in the neighborhood, in fact, of the caudal fin.t 
Jaekel infers that a dorsal fin could hardly have been present 
in Menaspis. If, however, the present explanation is just, a 
dorsal fin may well have existed, although it has not been pre- 
served in the type fossil. Its position is suggested by a dotted 
line in the restoration, DF, and the line of shagreen denticles 
shown in the fossil may have passed beside it, as in the case of 
chimreroids, both living and. fossil. 
The dental plates shown in the Berlin specimen, together 
with the entire fossil, will, it is to be hoped, be shortly figured 
by professor Jaekel, so that their more definite relations (e.g. 
to Deltodus and similar forms) may be accurately determined. 
I may, however, be permitted to note that they are strikingly 
chimaeroid in character, reminding one of Rhynchodus, al- 
though showing no conspicuous tritoral areas. In any event, 
the number of these plates is but four, as in the Devonian 
chimaeroid. 
Menaspis and its Relation to Chimaeroid FtsJies. 
If Menaspis, a Permian form, be closely related to chimae- 
roids, it possesses the interest of being the earliest representa- 
tive of til is ancient group whose body structures are preserved. 
And that it is essentially chimreroid is shown from the follow- 
ing grounds : 
(i) Resemblance to Myriacanthids. — Thc'^^: Mesozoic 
chimreroids possess a series of lateral head spines which agree 
essentially with those indicated by M.S., C C- and O. in the 
present restoration, Fig. lA. Especially convincing is the sim- 
ilarity of the anterior lateral spines in myriacanthids and Men- 
aspis. In the later form, however, the extreme rim of the 
* The left pectoral fin in the first specimen appears to hare been bent 
under the body, and has been partly exposed by the breaking away of the 
upper portion of the fossil, judging from Jacket's figure. 
t He does not explain, however, how this tallies with his view that Men- 
aspis was ray-like in habit. 
