24 



deeper than in papilio, and the under point only is spinous. 

 The supra-scapular and coracoid bones have the same 

 form as in papilio, viz., they have a central ridge, which 

 ends in an acute point, and the surface is rough, as in the 

 other bones of the head. The opercular spines have no 

 such ridge proceeding from them. The humeral bone is 

 oval, and smoother than any other bones about the gill- 

 opening or head. 



The spinous tips of the interosseous bones which arm 

 the dorsal furrow, are twenty-two on each side, and are 

 acute and trenchant, e.Kcept three or four anterior ones, 

 which are more or less compound. The sj^inous scales of 

 the lateral line corres])ond with the description given of 

 those of Tr. papilio, but the chief spine of each is larger 

 and more trenchant than the lateral si)inus of any Trigla 

 of which I have seen specimens or representations. In 

 plate XVI., figs. 3 and 4, the scales are turned upside down, 

 and they belong to the left side of the fish. They cor- 

 respond in number with those of papilio, being fifty- five. 

 The lateral line forks on the caudal fin very remarkably. 



The scales of the body, when in situ, present small 

 rhomboidal or nearly rectangular disks. When detached, 

 they have generally a dilated, fan-streaked, five or six- 

 lobed base, concavely curved sides, and a heart-shaped, 

 apiculaled disk, with an acute line or ridge from the apex 

 to the centre. In some parts, near the lateral line for in- 

 stance, the scales are oblique, and have more elongated 

 tips, and on the back some have two points. The concen- 

 tric lines of structure are very indistinct, especially near 

 the edges of the scale, which ai-e not toothed, their struc- 

 ture being apparently ctenoid* The scales of Tr. pa- 

 pilio are described as being nearly like the above, but with 

 two points ; those of phalatna and sphinx have rounded, 

 not hollow sides. Judging from the figure of papilio, in 

 the Hisloire de.s Poissons, the scales on the flanks of pleura- 

 cant hi ca are smaller than those of any of the species with 

 which we have compared it. 



The first dorsal is less rounded, and has a more parabolic 

 outline than that of papilio. The spinous rays are not so 

 irregular and suddenly bent. The third spine is the tall- 

 est, and the first two are serrated in front by a single row 

 of compressed teeth. The last rays of the second dorsal 

 and anal are divided to the base. 



The specimens have been greatly injured by the deterio- 

 ration of the spirit in which they were immersed, so that 

 the fin-membranes have nearly perished, and the tints of 

 colour are quite lost; but there appear to be some traces 

 left of a black spot on the fourth, fifth, and sixth spines of 

 the first dorsal. 



The air-bladder is of an oval form, and of the size of a 

 small pea. It is divided for nearly a third of its length 

 into two conical lobes, one of which is obtuse, the other 

 more pointed. At the other end of the bladder there is a 

 short, narrow, cylindrical projection, which divides the two 

 lateral muscles that fringe the viscus. 



The specimens are six inches long, of which the head 

 forms exactly one-fourth. 



* By mistake, a second spinous scale from the liiteral Hue was drawn, 

 instead of one of the smaller ones from the flanks. 



The air-bladder is in length 0'31 inches, and in breadth, 

 0.-22. 



Hab. Sidney Cove, Port Jackson. 



Datnia .' CAUDAViTTATA. Richardson. 



Ch Spec. D. dorse lateribnsque macnlis parvis crebris 

 nigro-fuscis aspersis ; pimni dorsi guttata et antice ad 

 marginem maculo iiigro noiatd ; pinna c<iud<s utrinque 

 nigro fascial a. 



Radii:— Br. 6— 6: D. 13|9 ; A. 3|8; C. 13|; P.15;V.li5. 



PlateXVIIl., figs. 3, 4, 5. 



This fish differs from the typical Datnia argentea, in 

 having more slender dorsal spines, and a porous lower 

 jaw; and from the group of Therapon, Datnia, Pelaf.es 

 and Helotes, in its air-bladder being simple, and not di- 

 vided by a narrow neck into two parts. The air-bladder 

 of our specimen is an inch and a quarter long, very obtuse 

 at one end, and tapering to an acute point at the other. 

 Its thick end is marked b}' two shallow furrows, producing 

 three slightly jirominent rounded lobes. Its coats are 

 nacry, and very distinctly fibroins, the outer layer of fibres 

 encircling the viscus transversely, and the inner one longi- 

 tudinally. In the condition in which the specimen was, 

 having been long macerated in spirits, these fibres sepa- 

 rated by a touch. The anal orifice is small, with plaited 

 lips, and immediately behind it there is a minute tumid 

 papilla, not raised above the neighbouring level, but 

 bounded posteriorly by a deep sinus. This papilla is 

 pierced by an orifice, which permits a bristle to pass into 

 the abdomen, but the intestines having perished, the origin 

 of its duct could not be ascertained. 



The height of this fish is equal to one-third of its total 

 length, being proportionably less than in D. argentea. 

 The thickness of the body is about a third of the height, 

 and the head forms about a fourth of the whole length. 

 The profile ascends obliquely, from the rather acute snout, 

 almost in a straight line to the nape, where it rounds off 

 into the dorsal line, whose summit is at the fourth or filth 

 dorsal spine, and opjiosite to the attachment of the ven- 

 trals.* The eyes round, moderately large, and close to 

 the profile, without interfering with it, are nearly a 

 diameter of the orbit apart from each other. The jaws, 

 gill-membrane, preorbitar, and the top of the head, back 

 to the temples, are scaleless. Two acute, smooth ridges 

 run from the nostrils to the scaly surface on the hind 

 head, about as distant from each other as each of them is 

 from the edge of the orbit of the same side. A mesial 

 ridge commences anteriorly, but sinks to the level of the 

 skull between the eyes, reappearing again behind these 

 organs, and running well back on the scaly nape. The 

 posterior frontal is marked immediately behind the eye by 

 some short, branching, elevated lines, turning obliquely 

 outwards. These ridges are all smooth, and are nearly- 

 concealed by the integuments in the recent fish. 



The intermaxillaries are scarcely protractile ; but the 

 raaxillaries, except a very small corner, can be concealed 



* In Datnia argentea, the ventrals are farther forward. 



