FISHES — EMBIOTOCOIDAE — EMBIOTOCA JACKSONI. 169 



the orbit is the most extensive and contains the largest scales of that region. The preopercle 

 is provided with an expanded membranous limb. The opercle, sub and interopercle, are 

 covered with conspicuous scales considerably smaller, however, on the interopercle than on the 

 two other pieces, the line of union of which is not discernible exteriorly. The branchiostegal 

 rays are entirely concealed under the interopercle. 



The relations which exist between the length and the depth of the body may be deduced from 

 an inspection of the figures. The section across the line of greatest depth (fig. 2) will also 

 serve to give a better idea of the thickness than any description could convey. 



A line dropped vertically from the origin of the dorsal fin would intersect the middle of the 

 base of the pectorals. The base of the spinous portion is about one-third shorter than that of 

 the soft. The membrane uniting the spines is emarginated to nearly the half of the height of 

 these rays, the tips of which exhibit a membranous flap, being a continuation of that membrane 

 along their posterior edge. The articulated rays are bifurcated three times ; the first bifurcation 

 subdivides each ray for nearly the two-thirds of their length, whilst the third afi'ects but a few 

 of the central ones. The extremities of the posterior rays extend about to the middle of the 

 length of the peduncle of the tail. The caudal fin is comprised a little over five times in the 

 total length of the fish. Its rays subdivide five times, beginning from near their base and 

 gradually superadding one another, when the fifth subdivision is observed towards their 

 extremities and still quite conspicuous. The anterior spiny rays of the anal fin are but little 

 conspicuous, partly concealed by a membranous envelop, obliquely inserted, and capable of 

 folding backwards close to the anterior soft ray. The figures will give a correct idea of their 

 proportional length. The soft portion of that fin is exteriorly sub-convex or sub-rounded, com- 

 posed of two sorts of rays : upon the anterior third of thin, slender, and undivided ones, whilst 

 in the remaining portion of that fin the rays are twice sub-divided, the first subdivision being 

 noticeable from the first third of their length. The extremities of the posterior rays extend 

 further backwards than those of the dorsal fin ; but the base itself extends further back, and a 

 line dropped vertically from the insertion of the last ray of the dorsal would intersect the anal 

 so as to leave ten or twelve rays posteriorly. The insertion of the ventrals is opposite the fifth 

 dorsal spiny ray. The extero-anterior margin of these fins is provided with a stout spine about 

 half the length of the adjoining articulated ray. The articulated rays themselves are sub- 

 divided three times, the first subdivision appearing at a short distance from their base. The 

 base of the pectorals has the shape of an arch obliquely situated upon the thoracic region. 

 These fins are broad and well developed ; the extremities of their longest rays extending beyond 

 the tip of the spiny ray of the ventrals and corresponding to a vertical line intersecting the 

 fourth articulated ray of the dorsal. The rays subdivide three times upon their extend. The 

 formula of the fins is as follows : 



Male: D IX, 22; A III, 10 + 17 = 27; C 4, 1, 6, 6, 1, 3 ; V I, 5 ; P 20. 



Female: D X, 21 ; A III, 10 + 16 = 26; C 4, 1, 6, 6, 1, 3 ; V I, 5 ; P 20. 



The scales being of medium size, we notice about seven rows of them between the lateral line 

 and the base of the dorsal fin, in advance of the dorsal furrow, and about nineteen between the 

 same spot and the base of the ventral fins. Fift}'-nine to sixty scales may be observed in the 

 lateral line itself. The dorsal furrow originates under the first articulated ray, extending to the 

 fifteenth, where it disappears. The sheath above it is composed anteriorly of three series of 

 22 a 



