614 CHARACTERISTICS OF THE ELACATIDS. 



Opercular apparatus normally developed; the operculum of a sub- 

 quadrate form, with its upper margin liorizoutal, the subopcrculum 

 under and i)artl3" behind the operculum, and tlie intcroperculum under 

 and mostly covered by the preopercuhnn. 



rreoperculum without a crest or armature. 



Branchial apertures continuous below, the hranchiostepal. membrane 

 being separated at the middle and partially overlapping in front. 



BrancMostegah seven, five belonging to the ceratohyal and two to 

 the epihyal. 



Dorsal furniture consisting of seven or eight short, stout, and free 

 spines, each with a special membrane, depressible in grooves, and a 

 long fin, with branched rays, commencing in advance of the middle of 

 the length. 



Anal fin shorter than the dorsal and coterminal with it, resembling 

 it in form, with a small spine in front, and preceded by a still smaller 

 free spine. 



Caudal fin strong, moderately forked behind, and with a number of 

 raylets above and below. • 



Pectoral fins normally developed, with a rather low base of insertion, 

 and i)ointed behind. 



Ventrals thoracic, approximated, each with a spine and five branched 

 rays decreasing inwards. 



Branchial arches normally developed, the last separated by a slit from 

 the hypopharyngeals. 



Gill-rakers short and stout. 



H}/pophari/npc((l bones separated, together forming an elongated tri- 

 angle, deeply cleft, and with the external submarginal crests extended 

 downwards into keels and continued into the posterior processes; third 

 epipharyngeals mushroom-like. 



The diagnosis thus given is the result of comparison of the cranium 

 with those of various generic types of the families of Scontbridw and Ca- 

 rangidw, all of which contrast remarkably with that oHElacate. The ver- 

 tebne are of the same type as those of the Scombroidea generally. It may 

 not be entirely needless to repeat that in the characteristics referred 

 to, as well as in almost all others, the Elacatids difter entirely from the 

 Echeneidiils. The affinities of the type appear to be as intimate, if not 

 more intimate, with the Carangids than with any other family, so far 

 as known; but it remains to be ascertained whether such is really the 



case. 



How different the cranial characteristics of the Elacatids and Eche- 

 neidids are may he juilgcd from a comparison of the illustrations of the 

 cranium of Elacate herewith given and those of the cranium of Echencis 

 published in the Proceedings of the IJ. S. National Museum for 1SSL> 

 (V. 5, pp. 5r)l-50(), pi. IL*). The differences of other parts are in some 

 cases of nearly equal value and in others of even greater Importance. 



