Page 341. 
340 ON THE ANATOMY OF PLOTUS ANHINGA, 
posterior (cervicalis ascendens, Meckel) entirely ceasing at the lower 
margin of the axis vertebra, in the tendon above described. 
There are other myological features deserving of special notice in ~ 
the thoracic and crural regions of the Darters. 
The great pectoral muscle is composed of two independent layers : 
—a superficial large one, arising from the inferior border of the 
sternum, its carina, and from the outer border of the fureula; and a 
deep one from the upper two-thirds of the deeper part of the carina, 
superficial to the pectoralis secundus, and from the symphysial half 
of the outer border of the furcula. The superficial layer is inserted 
by a broad linear attachment to the pectoral ridge of the humerus, 
whilst the deep layer ends in a rounded tendon which commences at 
the axillary margin of the triangular muscle, with which it is 
associated, and receives the fibres of the remainder of the muscle in 
its course to its attachment into the lower end of the pectoral ridge of 
the humerus, beyond the insertion of the lowest fibres of the super- 
ficial layer. In Plate [19] XXVII. this arrangement is clearly 
indicated. A condition exactly similar to this is observed in Phaéthon, 
Pelecanus, Sula, the Cathartide, all the Storks, and the Petrels, 
and in no other bird as far as I'am aware. In Phalacrocoraz it is 
not easily recognized. 
As in Phalacrocoraz and Phaéthon, but not in Sula or in Pelecanus, 
the biceps muscle of the arm sends a fleshy slip to the middle of the 
patagial tendon of the tensor patagii longus (Plate [19] XX VII. dD. s.). 
No trace of the expansor secundariorum* muscle could be de- 
tected. 
_ As in all the other Steganopods, the tensor fascia of the thigh 
does not cover the biceps cruris in the least. 
The ambiens is of fair size; it deeply grooves the large ossified 
patella; and some of the fibrous ligament overlapping this groove 
shows traces of ossification ; so that in aged birds the groove may be 
converted into a foramen, as is always the case in Phalacrocorax, where 
the thus formed foramen is far from superficial (vide Plate [20] 
XXVIII. figs. 5, 6, and 7). Im a specimen of Pelecanus rufescens 
the patella was not ossified. 
The semitendinosus is very large, composed of parallel fibres, and 
without any accessory head developed to join it. The femoro-caudal 
also, in all other true Steganopods, lacks an accessorius; it closely 
resembles that musele in Sula and Pelecanus, being separated from 
the obtwrator externus by a well-marked interval, which is not the case 
in Phalacrocoraz.t It is to be remembered, as I have had the oppor- 
* Vide ante, p. 193 (p. 323). 
+ Vide “ Proceedings of the Zoological Society,” 1873, p. 636. (Supra, p. 198.) 
