630 Bashford Dean Memorial Volume 



Plate VI. Allis's figure in his article (1923) appears to be in natural size, and Dean's 

 figure of a female fish in the original drawing measures 614 mm. (24.2 in.). This, it should 

 be noted, is just about the size of a young specimen taken by the Prince of Monaco at Ma' 

 deira, and pronounced by Collett (1890) to differ from adults only in the matter of size. 



Elsewhere it has been stated that there are in the Museum collection six adult 

 frilled sharks. What is the evidence from them as to protruding gill-filaments ? Three of 

 these sharks have been dissected by Smith (1937) who found that the gill-filaments did 

 not show externally. Similar conditions were found in the three undissected specimens. 

 None showed protruding filaments. We also have a head only, straight and well-preserv- 

 ed, but it shows no external filaments. As to the function of these slightly protruding 

 gill-filaments, one can infer that they make the gills of such adults as possess them, some- 

 what more efficient in respiration. 



From the data given, it is probable that some embryos of Chlamydoselachus (Fig- 

 ure 49, plate V) carry over into the adult stage remnants of their embryonic external gills. 

 But it is evident that most adults lack such protruding gill-filaments. For figures in which 

 they are absent, see Gudger and Smith's (1933) article on the natural history of Chlamydo- 

 selachus, wherein all known figures ot the whole fish and ot its head are reproduced. That 

 external gills sometimes occur in the adult Chlaynydoselachus is additional evidence of the 

 unpredictable characteristics of this primitive shark. Perhaps I cannot do better than to 

 quote Smith's summation (1937, p. 495) — "My outstanding impression of the frilled 

 shark is that it presents a strange assemblage of characters ranging from very primitive to 

 highly differentiated". 



