420 Bashford Dean Memorial Volume 



with regulating the passage of water, subservient to respiration, through the mouth into 

 the pharynx and out through the gill-clefts. When the spiracular canal and external 

 spiracular orifices of Chlamydoselachus are sufficiently large, doubtless a little water is 

 expelled through the spiracles. The oral breathing valve, the external openings of the 

 spiracles, and the gill-flaps have been described by Gudger and Smith (1933). In the 

 present paper I have already described the skeleton and muscles of the oral and pharyn- 

 geal region, and have noted the absence of a true spiracular cartilage. It remains to 

 describe the gill-filaments in relation to their supporting structures — in other words, 

 the gills — and to complete the description of the spiracles. The blood vessels of the 

 gills are described in the section on the blood-vascular system. My own observations 

 and drawings of the respiratory system of Chlamydoselachus are based on the three large 

 specimens in the collection of the American Museum of Natural History, and a fourth 

 large specimen kindly lent by Dr. E. Grace White. 



THE GILLS 



From the descriptions and illustrations in the article by Gudger and Smith (1933) 

 it is apparent that the gill-clefts of Chlamydoselachus are unusually large in proportion 

 to the si?e of the body. Some idea of the size of these clefts may be obtained from Text- 

 figures 4 (p. 339) and 77- Of his specimen Garman (1885.2) writes: "The gill-openings 

 are large; the first, when extended, will admit an object of four inches or more, and the 

 last will take one of two inches in width." In my specimen No. I, which is 1350 mm. long 

 (rather small for an adult), I find that the first gill-cleft (the one between the hyoid arch 

 and the first branchial arch) will admit the fingers and thumb of an entire hand; the 

 second, the four fingers as far as the palm; the third, the tips of four fingers; the fourth, 

 three fingers; the fifth, two large fingers; and the sixth, a thumb. These crude measure- 

 ments are sufficient to show the approximate size of the gill-clefts and the rapid decrease 

 in their size posteriorly. 



Garman's (1885.2) drawing (my Text-figure 77) of a gill-cleft and related structures 

 represents the fourth gill-opening on the right side. I have oriented the reproduction 

 of Garman's figure with the dorsal side uppermost; this brings the anterior holo branch 

 to the right. 



Each gill-arch of Chlamydoselachus affords attachment, distally, to one edge of 

 a crescentic plate, the gill-septum. The framework of the gill-arches is supplied by the 

 cartilaginous branchial arches, while the gill-septa are strengthened by very slender 

 radially directed cartilaginous rods, the branchial rays. Each branchial ray begins in 

 contact with the cartilaginous branchial arch and extends to the extreme edge of the 

 gill-septum, where it may cause a slight projection of the overlying membrane. In places 

 the margin of the gill-septum is strengthened by a delicate extrabranchial cartilage. 

 On each side of a gill-septum there are long narrow primary folds, the gill-filaments, 

 extending in a radial direction from the base of the gill-septum toward its margin (Text- 

 figure 77; Text-figure 78, a.f. and p.f.). On each broad surface of a gill-filament there are 



