CHAP TER Vii 
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 
1 
pr 
Fic. 91.—Petromyzon marinus. A, ventral ; B, lateral ; and C, dorsal, view of the head. 
br.cl.1, First branchial cleft ; buc. J, buccal funnel ; eye, the eye ; mth, mouth 3 NA.ap, 
nasal aperture; p, papillae; pn, pineal area; f}, #2, ¢3, teeth of buccal funnel ; 74, 
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 (F ig, 91, A’). 
The margin of the funnel is fringed by a series of short papillae, 
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