686 Bashford Dean Memorial Volume 



species the head is dorsoventrally depressed, but more so in H. quoyi than in H. francisci. 

 In both species, during growth the head becomes broader and less tall proportionally, but 

 only the ventral surface becomes actually flat. Because of differences in the shape of the 

 head, its bulk in the two species cannot be compared by ordinary measurements. 



From the total evidence it appears that most species of Heterodontus, in adaptation to 

 a bottom'dwelling mode of Hfe, have differentiated moderately in the direction of a broad' 

 ening of the head and anterior part of the body, accompanied by a lessening of the head 

 height and a flattening of the ventral surface of both head and body. These features 

 emerge in the course of development after hatching, and are not found in the very young — 

 a circumstance which leads us to infer that the more or less remote ancestors of this group 

 were not bottom-dwelling forms. From the meager information available, it is possible 

 that H. zebra has evolved in a different direction, tending to become eel'Hke in form. 

 This, also, is an adaptation to life on the ocean bottom. 



Another feature common to my specimens of both H. quoyi and H. francisci is the 

 slightly humpbacked appearance. This has already been mentioned as a possible generic 

 or family character. The hump is not due to an arched condition of the body. In each of 

 my specimens the greatest height of the dorsal surface, excluding the dorsal fins, occurs in 

 the region above the fifth gill'slit, which is also above the base of the pectoral fin. In the 

 pectoral region the ventral body wall is firm and the height of the body may be measured 

 accurately. The height of the hump may be computed by subtracting the head height 

 from the body height. Comparison of the height of the hump, in proportion to body 

 height in different specimens, may be made on a percentage basis. In my large female 

 specimen of H. quoyi the height of the hump equals 20 per cent of the body height; in the 

 small male specimen of the same species, 14.5 per cent. In the larger female specimen of 

 H. francisci the excess of body height over head height equals 21.8 per cent of the body 

 height; in the slightly smaller female, 10.6 per cent. It is noteworthy that in H. francisci 

 the smaller of two large female specimens has a hump only half the height of the other. 

 Judging from the drawings that have been published, this variability occurs also in H. 

 phillipi and H. japonicus. 



HETERODOKTUS GALEATUS GUNTHER 



The range of H. galeatus, so far as known, is limited to the waters of Queensland 

 and New South Wales. Whitley (1940) writes that in the northern part of New South 

 Wales this species (which he calls Molochophrys galeatus) tends to replace H. phillipi. 



H. galeatus was first described, from a single specimen, by Giinther (1870). The 

 first drawings of the entire fish are those of Maclay and Macleay (1879); they comprise 

 lateral, dorsal and frontal views. These drawings were made from a stuffed female 

 specimen (length not given) in the Australian Museum. A much better portrayal of 

 a lateral view, published by Whitley (1940), is here reproduced as Text'figure 20. Whitley 

 records that the length of sharks of this species is about five feet. Presumably this refers 

 to adult specimens. 



