CHAPTER VI 



EXTERNAL CHARACTERS OF CYCLOSTOMATA AND OF FISHES 



EXTERNAL CHARACTERS COLORATION POISON GLANDS AND 



POISON SPINES PHOSPHORESCENT ORGANS. 



In all the Cyclostomata the body is Eel-like in shape, the head 

 and trunk being nearly cylindrical, and the tail somewhat flat- 

 tened from side to side. In Petromyzon the head terminates in a 



br.cl.t 



FIG. 91. Petromyzon marinus. A, ventral ; B, lateral ; and C, dorsal, view of the head. 

 br.cl.l, First branchial cleft ; buc.f, buccal funnel ; eye, the eye ; mth, mouth ; na.ap, 

 nasal aperture ; p, papillae ; pn, pineal area ; t\ t 2 , t 3 , teeth of buccal funnel ; *, 

 teeth on the tongue. (From Parker and Haswell, after W. K. Parker.) 



ventrally-directed, funnel-like cavity the buccal funnel in the 

 roof of which the relatively small mouth is situated (Fig. 9 1 , A.). 

 The margin of the funnel is fringed by a series of short papillae, 



150 



