532 FISTULAKIDJ5. 



Skeleton. — The crown of the head is flat, striated, with a large 

 oblique groove behind each orbit. The principal frontal bones are 

 rather narrow between the orbits, widened anteriorly and posteriori}', 

 and forming projecting corners before and behind the orbit ; they do 

 not extend very far forwards, and form only the basal portion of the 

 rostral tube. The greater part of the upper surface of the snout is 

 formed by the ethmoid, whilst the vomer occupies the anterior fourth 

 or fifth. The prefrontal is situated in front of the orbit, elongate 

 and triangular. There is a deep and long groove on the side of the 

 snout for the muscles of the jaws ; its bottom is entirely ossified, and 

 formed by the tympanic, praeoperculum, entopterygoid, pre- and 

 meso-tympanic, these bones being exceedingly long. The entoptery- 

 goid and pretympanic are situated immediately below the ethmoid, 

 and provided with a crenulated ridge which is externally visible. 

 The bones which in other fishes constitute the bottom of the tym- 

 panic cavity below the orbit, are carried forwards before the orbit 

 in Fistidaria ; the epitympanic appears to be absent. The inter- 

 maxillary is only half as long as the maxillary, and has very short 

 posterior processes ; maxillary dilated posteriorly ; mandibula with 

 a deep longitudinal exterior groove. Turbinal bone very small ; 

 infraorbitals none. 



The process on which the humeral arch is suspended is very 

 long, reaching as far backwards as the operculum ; suprascapula and 

 scapula short, simple ; the humerus emits a process backwards for 

 the coracoid, another downwards for the radius or ulna, and finally 

 a third for its symphysis. There are three bones participating in 

 the symphyseal junction of the humeral arch : the nrohyal, which is 

 very elongate, the humeral and the pubic bones. Eachus and ulna 

 reduced to a single subcu'cular bone ; there are four narrow, longish 

 carpal bones. 



The shields which protect the anterior portion of the trunk are 

 the following : — 



1. A narrow strip along the median line of the back behind the 

 skull ; they are, in fact, confluent neural spines, belonging to the 

 anterior portion of the vertebral column, which we shall presently 

 describe. 



2. The pair of broader lateral dorsal shields are peculiar bones — 

 separated processes of the occipital bone — similar to those we have 

 observed in Mugil, where, however, they are not separated from 

 the occipital, and arise more outwards than in Fistularia. These 

 shields are the longest, provided inferiorly with a ridge, which is 

 prolonged and extends far backwards between the muscles of the 

 back. This ridge is flexible, and does not iaterfere with the lateral 

 movements of the fish ; it appears to serve as a base for the attach- 

 ment of muscular fibres. 



3. The narrow shield on the side is the coracoid, and composed of 

 two bones, the posterior of which is somewhat dilated and fixed to 

 the lateral dorsal shields. 



4. The ventral shields are the pubic bones ; their posterior half is 

 broadest, porous inferiorly ; they are narrower before the middle, 



