The Squamipinnes 409 
yellow, is common in Polynesia; Zebrasoma veliferum, cross- 
barred with black, is also common. 
Ctenochetus (strigosus), unlike the others, is herbivorous and 
has its teeth loosely implanted in the gums. This species, black 
with dull orange streaks, was once tabu to the king of Hawaii, 
who ate it raw, and common people who appropriated it were 
put to death. 
In Xesurus the caudal lancelet is replaced by three or four 
bony tubercles which have no sharp edge. Xesurus scalprum 
is common in Japan, and there are three species or more on 
the west coast of Mexico, Xesurus punctatus and Xesurus 
laticlavius being most abundant. 
In Prionurus (microlepidotus) of the tropical Pacific the 
armature is still more degraded, about six small plates being 
developed. 
In Acanthurus (Monoceros, naseus), the unicorn-fish and its 
relatives, the ventral fins are reduced, having but three soft rays, 
the caudal spines are very large, blunt, immovable, one placed 
in front of the other. In most of the species of Acanthurus 
along, bony horn grows forward from the cranium above the 
eye. This is wanting in the young and has various degrees of 
development in the different species, in some of which it is 
wholly wanting. The species of Acanthurus reach a large size, 
and in some the caudal spines are bright scarlet, in others blue. 
Acanthurus untcornts, the unicorn-fish, is the commonest species 
and the one with the longest horn. It is abundant in Japan, 
in Hawaii, and in the East Indies. 
Axinurus thynnoides of the East Indies has a long, slim body, 
with slender tail like a mackerel. 
Suborder Amphacanthi, the Siganide.— The Amphacanthi 
(augi, everywhere; akavla, spine) are spiny-rayed fishes cer- 
tainly related to the Teuthidide, but differing from all other 
fishes in having the last ray of the ventrals spinous as well as 
the first, the formula being I, 4, I. The anal fin has also six 
or seven spines; and the maxillary is soldered to the premax- 
illary The skeleton is essentially like that of the Acanthu- 
rid@. 
The single family, Siganide, contains fishes of moderate 
size, valued as food, and abounding about rocks in shallow 
