WELLBURN : OX THE GEXUS MEGALICHTHYS, AGASSIZ. 55 
Lateral Line. — I have not seen any evidence of this "sense 
organ," but it probably arises at a point on a level with the 
upper border of the operculum and traverses a longitudinal series 
of scales to an indetermined point on the caudal pedicle. 
Shoulder Girdle. — The pectoral arch exhibits well developed 
membrane bones, there being a large clavicle (Fig. C, PI. XIX.) 
and a smaller infra clavicle (Fig. D, PI. XIX.). A supra 
clavicular element was in all probability also present (as is the 
case in some other members of the order), but not having seen 
the bone I am unable to offer any opinion as to its characters. 
Fins. — (a) Faired fins. These were represented by the 
" Pectoral " and " Ventral " fins, the latter being abdominal in 
position. 
(1) Pectoral fins. These fins are obtusely lobate, and their 
superficial characters are beautifully shown in a specimen in the 
Science and Art Museum, Edinburgh (PL XYIL, Fig. B), and 
also in the fine fish in the Leeds Museum (see Fig. C, PI. XVII.). 
Characters. — (a) Superficial. At the base of the fins are 
a series of large scales, which are continued along the post- 
axial and preaxial borders, the space between these being occupied 
by smaller scales arranged in many parallel rows. {h) The 
internal skeleton is, as pointed out by Prof. Miall,^ indicated 
in Magalichthys, as in other fishes with lobate fins, by the 
external characters, the larger or fulcral scales covering the more 
rigid, and the smaller the more flexible parts of the internal 
structure (in the nearly allied family Rhizodontida? this character 
is clearly indicated in a pectoral fin of Strepsodus, which is in 
the Science and Art Museum, Edinburgh). The lobe of the fins 
seems to be, as pointed out by Mr. A. Smith Woodward, sup- 
ported by an endoskeletal cartilage (covered with a thin layer of 
dense bone. Cope), arranged on the plan termed archipterygial by 
Gegenbaur ; the axis being shortened, whilst the parameres of the 
one side are atrophied, those of the other border enlarged. There 
is thus no di- or tri-basal arrangement of the cartilages as in 
* Quart. Joum. Geo. Soc, Vol. XL,, p. 347. 
