54 WELLBURX : ox THE GEXUS MEGALICHTHYS, AGASSIZ. 
along with Osteolepis, Thursius, Dipterus, and Glyptopomus in the 
family Osteolepidse, and in this view Dr. Traquair seems to 
concur."^ 
Structure. — The body is much elongated, being about five 
times the length of the head, rounded and covered with rhom- 
boidal scales which run in obliquely sigmoidal parallel lines 
from before backwards, the greatest obliquity being on the 
dorsal and ventral surfaces, the scales becoming smaller on the 
latter surface. Well marked ridge scales present (at least) in 
the posterior half of the fish, where they pass some little distance 
on to and strengthen the anterior basal portions of the unpaired 
fins : they also pass for some distance on to and strengthen the 
upper lobe of the caudal fin. 
Scales. — The superior surface is divisible into an anterior 
or covered, and a posterior or exposed, portion (PI. YIIL, Fig. G). 
The anterior covered area is smooth and covered with a thin 
layer of non-corpusculate bone or kosmin, and is crossed by a 
grove which runs more or less parallel with the anterior and 
superior edges of the posterior or exposed portion. The "overlap" 
of the scales is from above downwards and backwards. The 
posterior exposed area is rhomboidal in form and is covered 
with a glittering layer of ganoine which ceases on the sides with 
abrupt rounded margins which dip down to and slope to the 
surface of the scale. This part of the scale is deepest at the 
centre, and on section is seen to be composed of non-corpusculate 
bone, tufts, capillary tubes and the upper series of the haversian 
canals (Williamson). The internal surface is smooth with the 
exception of an elongated ridge or boss (not present in J/. Icbvis 
Traquair) which runs more or less vertical to the axis of the 
bod}^ of the fish, and is situated between the anterior border 
and the centre of the scale. 
The Haversian system is in direct communication with the 
scale surface giving rise to the wide pores. 
Geo. Mag., Dec. III., Vol. VIII., Xo. 321, p. 123, Mar. 1891. 
