: ON THE ANATOMY OF PLOTUS ANHINGA. 337 
lower anterior. In further verification of this, it may be stated that 
in P. anhinga the bony bridges do not éxist, and yet the kinking is 
most strongly marked. 
Myologically the cervical region of the Darter is very peculiar, on 
account of the great concentration of its muscular mschanism towards 
the thoracic end of that segment of the body, the tendons from them 
running lengthy courses up the neck. The anterior and the posterior 
cervical muscles will be considered separately. 
Anterior cervical region.—Normally in birds, the longus colli anterior 
or great front flexor muscle of the neck, commences as a series of 
thin tendinous slips from the middle of the bodies of the first two or 
three vertebrae which carry complete ribs (true dorsals). The fibres 
diverge and ascend in such a manner that they form a bilateral 
_median mass acutely triangular at its lower end. They receive con- 
tinual accessions from the bodies and hemapophyses of the cervical 
vertebre, ending in slips which are attached, successively, to the 
apices of the anterior transverse processes three or four higher than 
the vertebre whence they sprang. Through the whole length of the 
7 cervical region they are of very similar mass, and therefore help 
to maintain the otherwise fairly uniform diameter of the vertebral 
: column*. 
4 In Plotus this uniformity is considerably disturbed, irrespective of Page 338, 
the above-described kink, by the excessive development of the longus 
colli in its lower almost interthoracic portion, as well as, though 
to a less degree, by the enlargement of the longus colli posterior 
behind. 
In Plotus anhinga, as above stated, there are 20 cervical vertebre. 
A small slip of the longus colli arises from the body of the third 
dorsal vertebra, which is inserted into the transverse process of the 
17th cervical. Above, and in contact with this, is another similar 
slip. to the 16th cervical. From the bodies of the 2nd and 1st dorsal 
vertebra, as well as from the antero-median portions of the six lower 
cervical vertebre,.a large muscle arises on each side, in layers (some- 
what resembling the layers formed by the basally expanded petisles of 
an onion bulb)—the lower being partially enclosed in the upper— 
which ultimately form a bipenniform mass with a tendon running 
axially through it and continually receiving additions in the form of 
outer coverings of tendinous tissue arising from the enclosing muscles, 
till it forms a strong single tendon which courses up the front of the 
neck, close to the middle line on each side, to be inserted into the down- — 
ward-directed, peculiarly long hemapophysial spine of the 8th cervical 
- Relay facie 3 ele atl 
* Vide Owen on Apteryz, “Transactions of the Zoological Society,” vol. III. 
Pl. XXXIII. p. 310. 
Z 
