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Bashford Dean Memorial Volume 



ventral views reproduced in Plates III and IV. where they seem to be growing on both 

 sides of each slit. That this is a fact, I have proved by microscopic examination of the 

 head of an embryo about 45'mm. long found in the Dean material in the Museum. This 

 specimen had been fixed in bichromate of potash and under the binocular microscope 

 showed filaments on both the anterior and posterior sides of every arch save the hyoid — 

 and some protruded even from the spiracle. These external filaments are somewhat better 

 developed in the 103'mm. fish (Figures 41-43, plate IV) than in any younger embryos. 

 But even here they are hardly so well-grown as those in Scammon's 20.6'mm. Squalus 

 (his Fig. 28, tab. III). 



Among the embryos loaned from Columbia University for this research, I could for 

 a long time find no specimen with gill-filaments longer than those of the 46-mm. young 

 (Figures 28-30, plate III) and of the 103-mm. fish (Figures 41-43, plate IV). However, 

 one day in examining the egg with the split yolk (referred to previously) as having a cap- 

 sule with the curious tendriliform process seen in Figure 13, plate I, I removed the crum- 

 pled shell, and to my great surprise and pleasure found the little fish with long filaments 

 now to be studied. 



This specimen (71-mm. long), as seen in Text-figure 32, has longer and more profuse 

 external gill-filaments than any young Chlamydoselachus figured by Dean. This will be 

 noted at once when Text-figure 32 is contrasted with Figure 41, plate IV (the 103-mm. 

 specimen). It is impossible to measure these filaments since they are more or less sinuous, 

 and sometimes spirally coiled. Due to their being tangled, they sometimes appear to be 

 branched, but under the binocular microscope this is seen to be an optical illusion due to 

 their overlying each other. For comparison's sake, there is introduced here, as Text-figure 

 33, Scammon's figure of his 28-mm. Squalus in about the same stage of gill-filament 

 development as the 7l'mm. Chlamydoselachus. Possibly if the filaments of the little 



Text-figure 32 

 A 7l'mm. frilled shark with a profusion of external gill-filaments. These are the longest found in any 

 specimen or drawing of this shark in this research. 

 Photograph by Charles H. Coles, A. M. N. H. 



