ELASMOBRANCHII — HOLOCEPHALI 



473 



were very small and simple. The caudal filament, whicli is 

 longer in older specimens than in the younger, and is not 

 developed at all in the youngest examples at present known 

 (Fig. 2*72, A), is not uptilted, although the lower lobe of the 

 caudal fin is much larger than the upper. Young forms have a 

 double row of stout spine-like denticles in front of the second 

 dorsal fin, and also in the interval between the latter and the 

 upper caudal lobe. Similar denticles are also present on the 

 \ipper surface of the head between the orbits (Fig. 272). H. 

 'mleighana is found in the North Atlantic. Individuals varying 



Fig. 272. — Young example of Harriotta raleighana, 4 inches in length. A, side view ; 

 B, dorsal view. (From Goode and Bean.) 



in length from 4 to 25 inches have been taken at depths 

 ranging from 707 to 1081 fathoms. A species of Harriotta 

 has also been recorded as occurring in Japanese waters.^ 



With the probable exception of Chimaera colliei the surviving 

 Holocephali are denizens of deep water ; hence their comparative 

 rarity and our almost complete ignorance of their habits. Young 

 forms of 0. monstrosa, ll to 5 inches in length, have been 

 dredged in the Faroe Channel at depths from 505 to 555 

 fathoms ; ^ and the youngest specimen of Harriotta was obtained 

 from 991 fathoms. Egg-cases are rarely obtained, and then 

 only from considerable depths. It is therefore reasonable to 



' Milsukuri, Zool. Mag. Tokyo, 1895, quoted in Hat. Sci. viii. 1896, p. 10. 

 2 Giinther, Chall. Reports, Zool xxii. 1887, p. 12. 



