116 



keep Psammoperca distinct, without venturing to decide 

 whether the group ought to be considered as of generic 

 value, or, as Cuvier has done in similar cases, merely as a 

 minor division. The blunt granular form of the minute 

 teeth, the form and structure of the preopercukim, the 

 scaliness of its imperfect inferior disk, and the deep notch 

 of its dorsal, are its most obvious external differences from 

 Centropristes. 



The following is a summary of the principal characters 

 of Psammoperca. 



Piscis acanthopterygius efamilid Percidarum. 



Dentes premaxillarmn, mandibulce, vomeris, ossiumque 

 palati minuti, rofundati, numerosissimi, conferti: canini 

 nullL 



Os preorbitale integerrirnum, simul ac nasus et man- 

 dibula iioromm, squamisque carens. Maxillae partim 

 squamis minutis iectcs. Genae operculaque prorsus squa- 

 inosce. 



Prteoperculum disco inferiori arclo squamis exiguis te- 

 neris iecto, margiiieque integei riiim niiiiii/iim.; anguloque 

 ejus in spinavi acutam decurrenti ; liiiihoqite erecto acute 

 pectiimto-dentato. Operculum spina gracdi, solitarid ar- 

 vtatum, lobo memhranaceo desinens. 



Anus medianiis. 



Squamae ptenoidea, basi flabellaiim sulcaUe. Linea la- 

 teralis aritice arcuata. 



Corpus compresstim, a latere ellipticum. 



Os humile, terminale. 



Membrana branchiostega radiis septem sustentata. 



Pinna dorsi profunde emarginata, spinis validis, (sque 

 ac pinna ani in thecd squamosa movens. Pinnae ventris 

 sub-axiUas pinnarmn pectoris positce ; squamis longis, 

 compositis extra interque fuUce. Pinna caudae valde ro- 

 tundata. Membranae omnium pinnaruni squamis teneris 

 arete appressis obrelatcB ; prwter membranam spinas dorsi 

 interpositam in qua squamce ordinatce juxta spinas tan- 

 tum adsunt. 



Psammoperca datnioides. Richardson. 



Radii:— B. 7; D. 8|12; A. 3|9 ; C. 15|; P. 15; V. 1|5. 



Plate LVII., figs. 1, 2. 



Body compressed, profile elliptical, its height about the 

 middle rather exceeding a fourth of the length of the en- 

 tire fish. The length of the head is more exactly a quarter 

 of the total length. Orifice of the mouth rather small, low 

 and terminal. The profile rises evenly, and with a slight 

 convexity, at an angle of .37° from the tip of the snout to 

 the beginning of the dorsal, which is at the first third of 

 the whole length of the fish ; and gradually joins the arch 

 of the back, whose summit is towards the end of the 

 spinous dorsal, or a very little before the middle of the 

 fish, caudal included. The curve of the belly is much 



more flat anteriorly, but posterior to the anus the ascent 

 to the trunk of the tail is equal to the descent of the back. 

 Height of the tail between the three vertical fins contained 

 twice and one half in the greatest height of the body. 

 Orbit placed near the profile, oval and rather large, its 

 greater axis being equal in length to one-fourth part of the 

 length of the head. Forehead between the orbits flat, not 

 equal in width to the vertical diameter of the eye. Nos- 

 trils, two round openings on each side, in a smooth mem- 

 brane, which reaches from the orbit to the end of the 

 snout, the posterior and larger opening being close to the 

 eye, and the anterior one near the fore comer of the pre- 

 orbitar. Mouth rather small, cleft horizontally to beneath 

 the fore part of the eye. Premaxillaries slightly pro- 

 tractile. Maxillary stouti.sh, dilating gradually towards 

 the lower end, which is truncated, passes the corner of the 

 mouth, and moves over the limb of the lower jaw : it does 

 not glide under the preorbitar, and its posterior corner is 

 clothed with minute scales. Even flattish bands of minute 

 roundish or granular teeth arm the jaws, vomer, and edges 

 of the palate bones. The dental band of the inter-maxil- 

 laries is broadest, and a little convex, and the more exterior 

 teeth are a little larger than the interior ones. On the un- 

 der jaw the band is much narrower, while on the small 

 three-cornered clievron of the vomer, and the edges of the 

 palate bones, the teeth are still more minute, but have the 

 same granular form. Roof of the mouth plaited poste- 

 riorly. 



Preorbitar meniscoid, with a slightly convex entire edge ; 

 its disk is widest under the posterior nostril. Rest of the 

 suborbitar chain very narrow. The scaly integument ter- 

 minates in a convex line between the eyes; the .snout, 

 whole of the suborbitar chain and lower jaw being covered 

 by porous skin. The cheek and gill-j)ieces are wholly 

 seal}'. Between the curve of the preoperculum and the 

 eye there are about eight rows of scales, and also several 

 rows on the inter-operculum, which graduate into smaller 

 scales on the adjoining bases of the gill-rays. The scales 

 of the operculum almost equal those of the body in size. 

 Small tender scales cover the lower limb of the preoper- 

 culum, a very narrow line of membrane showing obscurely 

 beneath them. When the integument is removed, the un- 

 der limb of this bone is seen to be composed of two thin, 

 even, edges of bone, with a deep furrow between, and 

 some pits in the bottom of the furrow. The upper limb of 

 the bone is strongly and acutely toothed in a very regular 

 pectinate manner, the teeth decreasing gradually in size as 

 they recede both ways from the middle of the series. The 

 angle of the bone is prolonged into a short, flat, spinous 

 point, between which and the lowest tooth of the upper limb 

 there is a small rounded notch filled with membrane. A 

 solitary, slender, subulate spine projects from among the 

 scales of the upper part of the operculum, the lobular tip 

 of the gill-cover and the narrow edge of the suboperculum 

 being membranous. Gill-opening pretty large, cleft for- 

 ward to beneath the middle of the eye. Gill-membrane 

 narrow, sustained by seven moderately long curved rays. 

 Disk of supra-scapular covered by small scales, its border 



