472 J. FRANK DANIEL 
In the right fin of my dissection this plate was separated into two 
parts so as to be included in the first line of the mesopterygial 
radials. The second row of the mesopterygium consists of six 
segments. The first segment of the third row of radials is fol- 
lowed directly by a similar more flattened segment which, in 
turn, abuts against a double row, the anterior of which is com- 
posed of four or five flattened plates, the posterior row having 
but four. The proximal segment in the fourth line of mesoptery- 
gial radials, like the third, is followed by a slightly shorter seg- 
ment which abuts distally against two rows, the posterior of 
which consists of four radials. The anterior plates have just 
been described. The proximal segment of the fifth row of radi- 
als is the longest of the series. It is continued distally by a 
pentagonal piece which fits against a double row of radials, the 
anterior proximal line of which was previously described, and the 
posterior row has but three segments capped distally by small 
cartilages. . 
The metapterygium (mt.p.) is a spatulate cartilage, the wider 
part of which points distally. From this ten or eleven rows of 
radialia diverge. The second two segments in the first two rows 
of these abut against double rows of radialia, each row usually 
consisting of two segments capped by smaller pieces; the third, 
fourth and fifth are similar except that the double rows are 
usually uncapped. The sixth to the eighth rows are of two seg- 
ments each, between which terminally single terminal cartilages 
abut. The proximal segments of the ninth and tenth radials 
of the metapterygium are followed by segments equal in length 
to themselves. Each one of these segments is capped by a single 
piece. In an older specimen the ninth and tenth radials were 
fused proximally and cleft distally. The eleventh radial gives 
evidence of being a fusion of two. The accessory cartilages 
accompany it; one appears at its apex, and another along its 
edge. 
2. The frame-work of the pelvic fin (fig. 29) in the female 
consists of a long posteriorly projecting basal cartilage, the 
basipterygium, to which radialia are joined. The basipterygium 
(ba.p.) in Heterodontus is separated into five sections, the proxi- 
