708 
EDWAltD W. SHANN. 
lu addition to tlie bony elements of tbe pelvic fin, namely 
the Basale metapterygii and the lepidotrichia (dermal 
fin-rays), which have been mentioned above, there are in 
addition three small nodules, the distal pterygiophores (see 
fig, 2, Pt.). The precise position of these nodules varies not 
only in different specimens, but in the right and left fins of 
the same specimen. The largest pterygiophore is placed 
invai’iably, so far as my observations go, between the dorsal 
and ventral halves of the ninth, or inner, fin-ray. The middle 
pterygiophore varies in position, but not infrequently occurs 
between the dorsal and ventral halves of the fourth fin-ray. 
The outer pterygiophore occurs between tbe dorsal and 
ventral halves of the third or second fin-ray. In one specimen 
the middle and outer pterygiophores were bound closely 
together and occupied the space between the third and 
second fin-i-ays. On warming each of these pterygiophores 
in turn in a weak solution of caustic potash, the inner was 
found to remain single, but the middle and outer split fairly 
readily each into two distinct nodules. That all these several 
portions are ossified is indicated by the fact that they 
effervesce when placed in dilute hydrochloric acid. 
Having now in mind the position and essential points in 
the anatomy of the pelvic fin of the salmon we shall proceed 
to locate and to describe the structure, known as the adipose 
lobe, with which it forms an intimate connection. 
(2) Anatomy of the Adipose Lobe. 
The lobe (fig. 1) lies in the angle between the pelvic fin 
and the body-wall in a position dorsal to and abaxialfrom the 
first, or outermost, fin-ray. It presents a vertical triangular 
surface when the fish is viewed from the lateral aspect, the 
acute-angled apex of the triangle being directed posteriorly ; 
at the proximal end its section is approximately in the fortn 
of an equilateral triangle, whose apex is directed inwards 
and is united to the body-wall of the fish ; at the aboral end 
the lobe is free and plano-convex in section, the convex 
