BY N. DE MIKLOUHO-MACLAY AND WILLIAM MACLEAY, F.L.S. 431 



enabling them to force their way under rocks and stones in pursuit 

 of these animals. A fine specimen of H. galeatus in the Macleay 

 Museum — a strong young female adult, had the dorsal spines worn 

 down to half their proper length, evidently in this way, and its 

 viscera were full of finely triturated Echinus tests indicating 

 pretty clearly how the grinding of the dorsal spines had been 

 effected. 



Explanation of Plate 20. 



Heterodontus Japonicus. Mel. 



Fig. 1. — Profile view of a spirit specimen of H. Japonicus in the 

 Australian Museum, Sydney • § of nat. size, the specimen 

 being about 1 9 inches long. 

 Fig. 2. — View of the same animal from above, also § of nat. size. 

 Fig. 3. — Anterior part of the head from the ventral side, to show 

 the arrangements of the nasal groove, the labial folds and 

 the anterior teeth. 

 Fig. 4. — Diagrammatic sketch of the teeth of the upper (Fig. 4, a.) 

 and the lower (Fig. 4, b.) jaws of H. Japonicus about 4 

 times the nat. size. The cyphers indicate the vertical rows 

 of teeth to illustrate the leferences in the test, 

 (The jaws not having been taken out, the drawing of the teeth 

 has been rather difficult, so that only a diagrammatic 

 sketch could be obtained. The spaces beneath the front 

 teeth are represented a little larger on the sketch than in 

 nature, but it is done on purpose to show more distinctly 

 the cusps of the teeth.) 

 Fig. 5. — One of the front 5 cuspid teeth of the middle row, 

 enlarged about 5 times. 



Lettering Followed throughout all the Figures. 

 a. — Superior oral fold. 

 b. — Inferior oral fold. 

 n.— External orifice of the nasal groove. 

 sp. — Spiracle. 



