The Embryology of Chlamydoselachus 625 



published figure of an adult Chlamydoselachus, and recording its form in their own four 

 specimens. But, unfortunately, they did not record the sex of each fish noted. This 

 I have done for all the specimens figured by them. Of these, 2 males and 4 females have 

 pointed tails, and one female has a tail that appears to be notched. Of the 6 adult speci' 

 mens in the Museum collection (4 used in previous researches, and 2 found since), all — 2 

 males and 4 females — have pointed tails, 3 straight and 3 drooping. 



THE HEAD OF THE ADULT SHARK 

 The lateral aspect of the head of Chlamydoselachus in both sexes, and with mouth 

 open and shut, is admirably portrayed in Figures 52 and 53, plate VI. What are needed to 

 make the portrayals complete are drawings of the dorsal and ventral aspects. Dean's 

 ''List" for "Adult" calls for "photo of head lateral and ventral". These I find, but I also 

 find two excellent drawings of the adult head seen from above and below. They will 

 now be described. There are no notes for these as there are none for the photographs. 



HEAD— DORSAL ASPECT 



The head in dorsal view is shown in Figure 54, plate VI. From the angle of the 

 jaws, the head narrows gradually to the rounded blunt snout — a marked contrast to 

 the broad blunt snouts of the tiger and whale sharks and to the keen'pointed ones of the 

 Isurid sharks. The eyes are set in shallow cavities. From the angle of the jaws, the head 

 widens to its maximum over the hinder edge of the first gill-cover. In all the gill'slits, 

 except the last, short external filaments are visible — as they are in the specimens repre- 

 sented in the fulHength drawings. Whether or not this head is that of the male fish, 

 portrayed in lateral view in Figure 53, plate VI, cannot be said, but it certainly is not that 

 of the female fish of Figure 52 on the same plate. Her first gill-cover looks as if it had the 

 edge bitten off. Also the space between the first and second arches is much wider than 

 that between the second and third, etc. In Figure 54, the widths of the openings are very 

 uniform save for the last ones at the bases of the pectoral fins. These fins are entirely 

 normal. Running along the back on either side is the lateral line. Of the latero-sensory 

 head canals, nothing can be seen save one curving gracefully in front of each first gill- 

 cover. No spiracle is shown. The opening was probably so small that the artist did not 

 find it. That this head seen in dorsal aspect is that of an adult Chlamydoselachus may 

 be judged by comparing it with the head of the l75-mm. specimen portrayed in dorsal 

 view (Figure 11, plate I). 



HEAD— VENTRAL ASPECT 



The ventral aspect of this same head (the figures have the same measurements) may 

 be seen in Figure 55, plate VI. Above and on either side of the mouth, the nostrils show 

 faintly. The almost terminal mouth, with some of the upper teeth showing, is very 

 prominent. So great is the front-to-back gape, that the angle of the mouth is a little 

 further than halfway back of the median point between tip of snout and hinder edge of the 

 first gill-cover. The throat has the skin plicate to allow for expansion when large objects 

 are swallowed. The gill-covers of the first arch are confluent across the isthmus or throat 



