The Embryology of Heterodontus japonicus 



711 



Maclay and Macleay (1879) state that Echini (Sea Urchins) form the chief food of 

 Heterodontus galeatus and probably of all the genus. The strong dorsal spines and the 

 prominent supraorbital ridges of these sharks enable them to force their way under rocks 

 and stones in pursuit of their prey. A fine specimen of H. galeatus in the Macleay 

 Museum had the dorsal spines worn down to half their proper length, evidently as a result 

 of scraping against rocks, and its "viscera" were full of finely triturated Echinus tests. 



My only information regarding the food and feeding habits of the Japanese Bullhead 

 Shark is derived from Dean's manuscript, from which I quote the following : 



It [Heterodontus japonicus] is a 

 bottom feeder, and is known to have 

 a varied diet: crustaceans, mollusks, fish 

 and sea urchins. With its formidable 

 dentition it crushes mollusks of consid- 

 erable size, and its well-worn grinding 

 teeth show that the crushing of shells 

 is a frequent habit. At first sight the 

 mouth appears extremely small, and one 

 gets the impression from the narrow 

 ends of the jaws which are exposed that 

 the fish is a "nibbler", and cannot open 

 its mouth widely. The photograph, 

 however (Text-figure 40) shows how 

 completely the shark may open its 

 mouth; and the captive fish is apt to 

 offer many demonstrations of this habit. 

 The jaws in such cases will sometimes 

 be snapped together noisily, indicating 

 great muscular leverage. In the case 

 figured, the fish was an old one and its 

 mouth was by no means in good order. 

 On either side of the large teeth were 

 tufts of sertularian hydroids; also there 

 were half a do2;en leeches in the neighbor- 

 hood, some specimens measuring about 

 2K inches in length. 



Text-figure 40. 

 View of the wide-open mouth of a new-caught Hetero- 

 dontus, presumably japonicus. Note the large grinding 

 teeth in the posterior part of the roof of the mouth. 

 From a photograph taken by Bashford Dean at Misaki, Japan. 



BREEDING SEASON 

 Concerning the Port Jackson Shark, Heterodontus phillipi, Maclay and Macleay 

 (1879) state that, if the accounts of the fishermen are to be believed, it is very slow of 

 reproduction — the females never having more than two eggs at a time and only one 

 brood a year. McCoy (1890) states that Cestracion (Heterodoiitus) phillipi never lays 

 more than two eggs at a time, and only once a year. He does not say how or where he 

 obtained his information. In view of the results obtained by Dean through examination of 



