336 



Bashford Dean Memorial Volume 



nation of this material has enabled me to fill in some of the most important gaps in the 

 hitherto available knowledge of the gross structure of Chlamydoselachus. Our knowledge 

 of this interesting fish is still incomplete, and one purpose of the present article is to 

 direct attention to the opportunities for investigation that still exist for one who is able 

 to secure favorable material. 



Since the anatomy of the lower vertebrates is of interest chiefly from the comparative 

 point of view, I have endeavored, within the limits imposed by practical considerations, 

 to point out some of the resemblances and differences between Chlamydoselachus and 

 other primitive sharks — particularly its nearest relatives, the Notidanidae. Fortunately 

 for my purpose one of these, Heptanchus maculatus, forms the basis of Daniel's (1934) 

 masterly treatise on the anatomy of the elasmobranch fishes — a volume which I have 

 found very helpful. 



For those who view this and similar undertakings from afar, it may be permissible 

 to state that only anatomists and embryologists realise how much the study of elasmo' 

 branchs has contributed to our understanding of the present structure and past history 

 of the human body. 



EXTERNAL CHARACTERS OF CHLAMYDOSELACHUS 



Since the external characters of the frilled shark have been described in detail by 

 Gudger and Smith (1933), only a few of these features which are of particular significance 

 for comparative anatomy need be considered here. 



GENERAL FORM OF THE BODY 



As compared with other sharks, Chlamydoselachus (Text'figure 1) is very slender. 

 Therefore it is pertinent to inquire what an elongate form of body means in the evolution' 

 ary history of a group of vertebrates. In general, the most primitive members of any 

 large and divergent group are only moderately elongate, while a high degree of speciali- 



Text-figure 1. 



Chlamydoselachus anguineus Garman, adult female, 1473 mm. long. 



After Dean, 1895, Fig. 92; redrawn from Gunther, 1887, PI. LXIV. 



