152 FISHES CHAP. 
In Fishes the characteristic shape of the. body is more or less 
that of a spindle, tapering at each end and somewhat flattened 
froin side to side; and, as a rule, the three regions of the body— 
head, trunk, and tail—pass almost imperceptibly into one another 
(Fig. 93, A). Nevertheless, there is great diversity of form in 
different Fishes. Compare, for example, the elongated, cylindrical 
shape of the Eels (which is perhaps associated with their habit of 
Fic. 95.—Tilapia dolloi. To show the external characters of an Acanthopterygian 
Teleost. A, side view ; B, the first branchial arch. a,f, Spinose part of the anal 
fin ; af}, soft rays; c.f, caudal fin; d.f, spinose portion of the dorsal fin; d.f?, 
soft rays ; g,f, gill filaments ; g.7, gill rakers ; 7././, inferior lateral line ; , nostril ; 
p-J, pelvic fin ; p.op, preoperculum ; pt.f, pectoral fin ; s./.2, superior lateral line ; 
t.s, transverse row of scales. (From Boulenger.) 
insinuating themselves into holes and crevices, and their undula- 
tory, snake-like movements when swimming); the compressed, band- 
like shape of the Ribbon-Fishes (Trachypteridae); the flattened 
bodies of those Fishes which habitually live and move on the 
bottom, lke the Skates and Rays; the thin, laterally-compressed 
bodies, often nearly as high as long, of the Flat-Fishes (Pleuro- 
nectidae), which always swim and rest on either the right or left 
side ; the almost spherical Globe-Fishes (7etrodon) which often 
float passively in the water; and the singular rectangular, 
coffin-like Coffer-Fishes (Ostracion). There is also much differ- 
ence in the relative proportions of the three regions of the 
body in different Fishes, as witness the enormous size and 
