150 



DR. J. MURIE ON THE WHITE-BEAKED BOTTLENOSE. 



Cetacea*, the orifice terminal. The bulbo-cavernosi, retractores 

 and erectores muscles are of enormous volume. 



To give an idea of the enormous volume of the infracaudalis, 

 the so-called psoas of some authors, I need but mention that its 

 fleshy belly measured 51^ inches long, with a breadth at the root 

 of 8 inches, and depth corresponding. "Within the abdomen 

 the diaphragm overlays it for more than a foot. The fleshy part, 

 as usual, covers nearly the entire space upon and between the 

 transverse process and the hsernapophyses or chevron bones. On 

 reaching the forty-fifth vertebra, strong tendons emerge from 

 its ventral surface ; but latterly and above the fleshy belly nar- 

 rows, and goes on to a point outside the sixtieth vertebra. The 

 tendons spoken of, some twenty or more in number, run back- 

 wards, but are enveloped in an aponeurotic sheath, and sepa- 

 rate one by one from this. 



Two or three of the last upper tendons unite and constitute 

 one strong thick cord. This proceeds back quite to the hind- 

 most caudal vertebra, where it expands slightly in an aponeu- 

 rotic form. 



This is essentially a powerful flexor of the tail. The upper 

 stronger tendons, carried to the tip of the vertebral column, act 

 the part of a long lever, analogous to the shaft of a screw pro- 

 peller. The inferior tendons act also on the tail, but in a 

 different manner from the upper ones, inasmuch as, their at- 

 tachment being from the middle of the chevron bones to the 

 last of the hgemapophyses, their power is distributed. They 

 nevertheless distinctly influence the movements of the caudal 

 fin or tail through their enwrapping sheath, which is directly 

 continued on to and intermingles with the glistening and 

 dense fibroid tissue composing the horizontal tail itself. I have 

 shown in Physalus and Gloliocephalus how the tendons are 

 packed and enwrap each other, both in a longitudinal view and 

 transverse section ; so 1 need add nothing further regarding them 

 here. 



The abdominal aorta is wide, its walls moderately thin, and, 

 as in other Cetaceans, there are intercostal plexuses. The series 

 of transverse branches which are derived from the aorta are 

 situate about J an inch apart, and nearly equidistant from each 

 other ; the secondary divisions commence | of an inch from the 



* Vide illustration of that of Delphinus tursio in Van Beneden's brochure 

 " De la Composition du Bassin des Cetaces," Bull. Acad. Belg. 2nd ser. tome xxv. 



