OF THE SKULL IN SHARKS AND SKATES. 233 



Fig. 2. Another embryo, 11 lines long, seen as an opaque object, X 14 diam. 



Fig. 3. The same, seen from below, X 14 diam. 



Fig. 4. The same, seen from above, X 14 diam. 



Fig. 5. The same, in longitudinal section, X 14 diam. 



Fig. 6. Part of fig. 1, X 24 diam. 



PLATE XXXV. 



Fig. 1. First stage. Side view of Pristiurus embryo, | of an inch long, X 20 diam. 



Fig. 2. The same, from below, X 20 diam. 



Fig. 3. Dissection, from above, of the same embryo, X 20 diam. 



Fig. 4. Dissection, from above, of a larger embryo (f of an inch long), x 20 diam. 



Fig. 5. Dissection, from above, of an embryo of ScyUiiim canicula (13 lines long), 



X 20 diam. 

 Fig. 6. Second stage. Dissection, from above, of a larger embryo of Scyllium canicula 



\\ inch long, X 14 diam. 

 Fig. 7. The same, dissected from below, X 14 diam. 

 Fig. 8. Part of fig. 6, X 30 diam. 



PLATE XXXVI. 



Fig. 1. Second stage. Side view of head of Scyllium canicula, partly dissected, from 



an embryo, 1 inch 2 lines long, X 12 diam. 

 Fig. 2. Vertical section of a somewhat larger embryo, X 14 diam. 

 Fig. 3. Third stage. Chondrocranium of a two-thirds-ripe embryo of tlie same fish, 



1 inch 8 lines long, seen from above, X 10 diam. 

 Fig. 4. The same object, seen from below, X 10 diam. 

 Fig. 5. The cranium without the facial arches; side view, X 10 diam. 

 Fig. 6. Section of head of the same, X 14 diam. 



PLATE XXXVIl. 

 Fig. 1. Third stage, continued. Skull of the same, seen from below, X 10 diam. 

 Fig. 2. Fourth stage. Adult Dog-fish, upper view of the skull, X 1 2 diam. 

 Fig. 3. The same, with facial arches removed, under view, X I2 diam. 

 Fig. 4. Section of head of the same, X 1^ diam. 

 Fig. 5. Part of same object, X 5 J diam. 



PLATE XXXVIII. 

 Fig. 1. Skull of adult Dog-fish, seen from below, X I5 diam. 

 Fig. 2. Side view of same, X I5 diam. 

 Fig. 3. End view of same, X 1^ diam. 

 Fig. 4. Vertical section of cranium, X 1^ diam. 



