ANATOMY OF BAL^NOPTERA ROSTRATA. 
225 
External to but connected with this muscle, a distinct slip of muscular fibres passed 
from the same origin to the posterior portion of the mastoid process, the lower fibres of 
which seemed to represent the sacrolumbalis muscle, while the anterior portion 
was probably the slightly displaced homologue and representative of the splenius 
capitis. 
Levator caudse, a very powerful muscle, was overlapped by the last described, with 
which some of its fibres were continuous ; it arose by strong fleshy fibres from the dorsal 
aspect of the transverse processes of the lumbosacral and caudal vertebrae about 5 feet 
anterior to the root of the tail ; it was inserted by eight strong flattened tendons, each 
of which measured from \ to f- of an inch in thickness, into the sides of the neural 
spines of the lower caudal vertebrae, expanding posteriorly into the fibrocartilaginous 
tissue which formed the substance of the lateral flukes of the tail. 
Depressor caudae major, an enormous muscular mass which formed the entire bulk 
of the posterior and inferior part of the body from the pudendal fissure to the base of 
the tail, and arose from the anterior surfaces of the bodies and transverse processes of 
all the lumbosacral and all the caudal vertebrae, and also from the ventral and lateral 
surfaces of the chevron bones. This muscle was divided into about nine subordinate 
bundles, each of which terminated in a round powerful tendon, which, at its origin 
from the muscle, measured about 1 inch in diameter; all these tendons passed back- 
wards, and expanding were inserted into the sides and anterior surfaces of the bodies 
of the caudal vertebrae, the last tendons expanding into the under surface of the sub- 
stance of the tail. 
Depressor caudse minor. — This muscle was similar to but smaller than the last 
described ; it arose below and external to it, from the anterior surfaces of the caudal 
vertebrse, extending as far forwards as midway between the last rib and the posterior 
extremity of the spinal column, and was inserted by roundish tendons into the substance 
of the tail, sending a few of the most anterior fibres to the most posterior of the caudal 
vertebrse immediately connected with that organ. 
The anterior or pectoral extremity, although it externally appeared but a solid single 
lancet-shaped organ, yet on examination was found to contain the rudiments of the 
various segments of the typical vertebrate upper extremity as found in the other orders 
of Mammalia, viz. scapula, humerus, radius and ulna, carpus, metacarpus, and phalanges. 
The muscles, as might be expected, were small, rudimentary, and undeveloped ; 
nevertheless it was not difficult to determine the position and homologies of those that 
were present. 
Among those of the shoulder. — The Deltoid was small, fleshy, and triangular in shape ; 
it arose from the upper half of the external flat surface of the scapula above the infra- 
spinatus ; the fibres passed outwards and backwards, converging towards the head of the 
humerus, into the anterior and internal surface of which they were inserted by a strong 
flat tendon ; its action was probably to advance the paddle upon the scapula. 
Teres major. — A flattish muscle, arose tendinous and fleshy from the inferior border 
mdccclxviii. 2 K 
