470 The Phylogeny of the Palmar Musculature 
strata. Thus the reptilian layers compared with those of the amphibia 
are as follows: 
Amphibia. Reptilia. 
Wl. Browkesenacheralia { Fl. brevis superficialis stratum superficiale. 
i I s { Fl. brevis superficialis stratum profundum. 
Fl. brevis medii stratum superficiale. 
Fl. brevis medius Fl. brevis medii stratum medium. 
| Fl. brevis medii stratum profundum. 
Fl. brevis profundus Fl. brevis profundus. 
Intermetacarpales Intermetacarpales. 
The flexor digitorum brevis superficialis—The stratum superficiale 
is a strong muscle arising from the surface of the volar cartilage and 
is 
Fig. 4. The stratum medium of the flexor brevis medius of Jguana. fbmj,, portion 
to the fifth digit; fbms°, portion of the stratum superficiale to the fifth digit; fds, 
line of origin of the flexor brevis superficialis; abm, abductor minimi digiti; p, the 
deep palmar aponeurosis and the profundus tendons; we, volar cartilage. 
aponeurosis, the line of the origin (Fig. 4, fobs) being somewhat curved, 
with its convexity directed distally and prolonged much more proxi- 
mally at its ulnar extremity than at the radial. Traced distally it 
divides into six portions, one for each of the four radial digits and 
two for the minimus. The portions for the second, third and fourth 
digits when traced distally are found to divide each into two slips 
which diverge to fade out in the fibrous tissue covering the sides of 
the metacarpo-phalangeal joint, allowing the profundus tendon to pass 
between them and become superficial. The portion to the pollex, how- 
ever, does not divide into two slips, but passes entirely to the outer 
side of the joint, the profundus tendon becoming superficial to its 
ulnar side, while in one of the portions to the minimus, although two 
