286 



Bashford Dean Memorial Volume 



others in the cloacal region, will be further considered in the article on the anatomy of 

 the frilled shark. 



DERMAL DENTICLES 



The placoid scales or dermal denticles cover the entire body, including the fins and 

 that part of the sclera which is exposed when the eyes are turned upward; also they line 

 the mouth, gullet, and branchial arches. In sharks generally, the skin with its close^set 

 denticles comprises what is called shagreen. The dermal denticles ot Chlamydoselachus 

 have been studied by two investigators, Garman and Rose. The former (1885.7, pp. 6 

 and 7) says : 



Over the entire body the scales are small and irregular in size and shape. On the flank 

 and belly they are polygonal plates, or depressed lumps . . . surmountedbyone, two, or three 

 sharp prominences, the median of which is stronger, in places becoming a keel. On the tail 

 this keel is produced beyond the base as a spine. This spine is very sharp, has three longi- 

 tudinal ridges, and is excavated slightly or flattened beneath. About the mouth and in 

 particular around its angles the spines are larger, more conical, and more erect — more like 

 teeth. [Carman's PI. VI, fig. 12 reproduced as our Text-figure 13]. Each of a few of these 

 scales has a small cusp near its base. In the mouth, just behind the last row of teeth, there 

 are spines which are more slender, and which have broader bases. . . . From each side of the 

 lateral line elongate scales with chisel-shaped or truncate ends reach out to meet similar 

 ones from the other side, thus forming a cover or protection for the canal. [Carman's PL 

 VI, fig. 10— our Text-figure 18.] 



The scales have been studied by Rose (1895) in connection with his work on the 

 teeth. These scales came from a 340-mm. (13.4'in.) embryo taken from the "uterus" of 



Text-figure 14 Text-figure 15 



Dorsal view of a placoid scale Lateralviewof a dermal denticle (xl30) 



(x 130) from the flank of a 340-mm. from the tail region of a 340-mm. 



uterineembryoof ChIam>ido5el(jchus. uterine embryo of Chlamydoselachus. 



After R6se, 1895. After Rose, 1895. 



Text-figure 16 



The scale seen in Text-figure 



15 in the same enlargement 



but viewed from beneath. 



After Rose, 1898. 



