284 



Bashford Dean M.emorial Volume 



made on specimens badly shrunken by long immersion in preserving fluids and much 

 crumpled by being curled up in containers. 



All the above notes pertain to adult females — Carman's and Collett's specimens and 

 our three. There are now to be considered our six embryos. Our two larger specimens, 

 a male 374 mm. long and a female 320 mm. long, have long been in strong formalin. The 



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Text-figure 12 

 The tropeic folds of Chlamydoselachus: A, of an adult from below ; B, of an embryo from below. In both, 

 the central dark line is the bottom of the fold, the white lines mark the top of the fold, and the outer 

 dark lines the outside bases of the fold. C is a lateral view of a part of the side of an embryo showing 

 the lateral line, the myomeres, and the side of the fold. D is a section of the tropeic fold in an adult, 



copied from Garman, 1885.2. 



keel in each is very marked, 3-4 mm. high, with only slight indications of a median groove 

 on its outer surface. However, our four small embryos (males, 305 mm., 245 mm. and 210 

 mm. respectively, and a female only 190 mm. in total length) all have well-developed keels 

 with equally well-developed grooves along the mid-line. In these embryos, especially in 

 our two larger, these keels are so marked as to give the abdomen of each a very definite 

 resemblance to the lower V-shaped hull of a racing yacht. 



To illustrate these structures we have had drawings made (Text-figure 12). The 

 legends to these make unnecessary any further description. The structure of these un- 

 usual organs will be further described in an article on the anatomy of Chlamydoselachus. 



As to the function of this curious structure, but two conjectures have been made. 

 Garman (1885.2, p. 3) first described this from a fertile female and stated that "the 

 prominence of the keel and its folds was looked upon as a possible sexual development, 

 appearing when the young are carried." However, its marked appearance in our male 

 embryos, plus the fact that such folds have never been found in any other shark even at 

 breeding season, completely disprove this conjecture. Collett suggested that possibly the 



