The Embryology of Heterodontus japonicus 757 



figure 21 . Some portions of the color pattern of Brevoort's specimen appear to be unique. 

 It is possible that an adequate collection of this species would reveal considerable varia' 

 tion in the color pattern in all stages of its development. 



A 280'MM. YOUNG HETERODO?{rUS JAPOKICUS 



This young female (Text-figure 65) belongs to the collections of the American 

 Museum of Natural History and was probably procured in Japanese waters by Bashford 

 Dean. It is one of the specimens used by Dean for the study of the developing teeth. An 

 incision leading from the mouth nearly to the first gill-slit was made in order to expose the 

 mouth cavity. This incision was closed by large stitches with fine white thread, but still 

 shows as an irregular line in the photograph (Text-figure 65). Two lines, both nearly 

 vertical but meeting at an acute angle, at the extreme anterior end of the snout, are mere 

 artifacts — creases in the skin — and have nothing to do with the olfactory organ. The 

 fifth gill-slit is smaller and less conspicuous than the others, both in the specimen itself 

 and in the photograph. The spiracular opening is still large enough to be sharply defined. 

 The parallel vertical grooves along the side of the body posterior to the gill-slits are less 

 numerous, less regular and less conspicuous than they are in the specimen represented in 

 Figure 84, plate VII, which is considerably younger. Some careful measurements of the 

 specimen under consideration are given in Table II. 



TABLE II 



SOME MEASUREMENTS IN MILLIMETERS OF A 280-mm. FEMALE 



HErERODOKTUS ]APOKlCUS 



Total length 280 



Greatest width of head (at first gill-covers) 44 



Greatest height of head (at posterior end supraorbital ridge) 35 



Greatest height of body (in a transverse plane passing through fifth gill-covers) 42 



Length of first gill-slit 17 



Length of fifth gill-slit 8 



Base of first dorsal overlaps base of pectoral 8 



Length of base of anal fin 16 



Distance between base of anal fin and ventral lobe of caudal 27 



Distance from tip to tip of extended pectoral fins 160 



Vertical distance from ventral surface to tip of extended first dorsal fin 100 



Most important for the identification of the species is the fact that the color pattern 

 of this 280-mm. fish is fairly well preserved (though it does not show well in the photo- 

 graph). The color pattern agrees in most respects with the color pattern of the younger 

 specimens portrayed in Figures 83 and 84, plate VII. If one ignored the color pattern and 

 depended entirely on Carman's key (page 663 of the present article) one would be very 

 likely to classify this specimen as Heterodontus pMUpi instead of H. japonicus. But the 

 differences in the color patterns of the two species are very great, especially in young 



