MYOLOGY OF THE ORNITHORHYNCHUS. 135 



processes of as many caudal vertebrae ; bej'oncl, it is iudistiuguishable 

 from the rest of tlie muscle. 



Flexor lateralis.— The smaller of the two perfectly distinct caudal 

 depressors is wholly ischio- coccygeal, arising definitely from the tu- 

 berosity of the ischium by a broad fleshy origin. It is a somewhat 

 square, entirely fleshy plane proceeding obliquely outward and down- 

 ward to be definitely inserted by about 3 digitations into the trans- 

 verse processes of as many coccygeal vertebrse, just in advance of the 

 origin of the caudo-tibial muscle. 



Depressor caudcB. — The principal flexor of the tail is the largest of 

 all, as well as the most complex in structure ; and doubtless, to judge 

 from the obliquity of its segregated fascicles, it subserves other 

 movements of the member. It arises, first, inside the pelvis just 

 behind the acetabulum, and at the junction of the haunch-bone with 

 the sacrum; it may be said, further, to take continuous origin theuce 

 to the tip of the tail, from the apices and under surfaces of all the 

 transverse processes. The fibres are very oblique ; except at first, in 

 fact, it may be regarded as a series of many such diagonal slips, partly 

 blended together. The under surface is invested with an extremely 

 dense glistening aponeurosis, made up of a number of obliquely set, 

 overlapping or imbricated laminae of fascia, each of which is the broad 

 flattened tendon of a muscular fasciculus. These aponeuroses com- 

 bined are the tendon of insertion of the muscle into the vertebral 

 bodies from near the base to the extreme tip of the tail. 



Besides the foregoing caudal muscles, there is a series of well 

 developed intertransversales ; and another set of smaller slips runs 

 along the articular eminences. The tibio-caudal muscle, although 

 attached to transverse processes, as it passes by them, extends to the 

 median line of the tail underneath, by a thin, broad, flat tendon that 

 lies external to the main flexor of the tail. 



III. Cervical Muscles : — Superficial, and not connected with ver- 

 tebrae or scapula. 



Under this head will be noticed the sterno-mastoid and principal 

 muscles of the hyoid apparatus. The fii'st named is double on each 

 side, unless one portion is " cleido-mastoid." The hyoid muscles ex- 

 hibit a remarkable tendency to run together, both by lateral blending 

 and by end-to-end joining, in several cases where among most animals 

 they are distinct. 



Sterno-mastoid. — The superficial portion is the larger: it arises by 

 a short flattened tendon from ("the mastoid" — Owen; inser- 

 tion destroyed), and forms a stout, somewhat flattened belly that 

 descends obliquely inward, exactly parallel with, and contiguous to, 

 the anterior border of the trapezius, to be inserted fleshy and by a 



