146 PROCEEDINGS OF THE ACADEMY OP 



deeply and acutely notched. The genus Glyphidodon, whose teeth are emar- 

 ginated, have al30 a short conic head and low (or narrow) preorbital bones. 



Er/SCHISTODUS DECLIVIFRONS Gill. 



The region of greatest height is at the sixth dorsal spine ; the height there, 

 exclusive of the dorsal sheath, -45 of the total length ; behind the vertical fins 

 the height equals -18, and at the lowest portion of the caudal peduncle -.15 of 

 the length. 



The outline from the dorsal fin to the nape is convex and very obliqne, then 

 rectilinear, and at an angle of 50 to the axis as far as the interorbital region, 

 which is transversely convex ; in front the profile is also nearly rectilinear and 

 at an angle of about 73 ; the snout, or rather jaw. is convex or curved inwards. 

 The length of the head forms a quarter of the length, inclusive of the median 

 caudal rays, and equals the height at the vertical of the pupil, but is a sixth 

 less than that at the vertical of the preoperculum. The nape is above the 

 hinder margin of the orbit. The length of the snout exceeds a third (9-25) 

 of the head's, and is twice as great as the greatest depth of the preorbital bone 

 and nearly three times (9 3J) as great as the depth at the angle of the mouth. 

 The preoperculum is entirely vertical behind, horizontal below and obtusely 

 angulated. The operculum forms about a third of the head's length (-81) ; the 

 operculum and suboperculum together are two and a third times (20 8|)~higher 

 than the length of the operculum. The eye is contained nearly three times (9-25) 

 in the length of the head, and the interorbital area is transversely arched and 

 exceeds the eye's diameter. 



The mouth is small and its periphery semioval ; the lower jaw is considerably 

 shorter than the upper. The supramaxillary bone ends under the anterior mar- 

 gin of the orbit. The lower lip has a free margin, but it is partially attached 

 at the symphysis. 



The dorsal fin commences at the vertical from the upper axilla of the pec- 

 toral fin ; its spinous portion nearly equals two-fifths (-39) and its soft a seventh 

 (14) of the total length; the spines progressively increase in a curved line 

 towards the fifth, the first spine equalling half the length of the ventral spine 

 (5) ; the fifth, from its hase, much exceeds (-13), and on its exposed part 

 nearly equals (-10) twice its length; thence they diminish towards the last, 

 which equals the length of the exposed part of the fifth. The soft part at its 

 middle equals the height immediately behind the fin ("18) and is much more 

 than twice as great as the length of the last ray (-7). 



The anal fin begins under the penultimate spine, and its soft part is similar 

 to and opposite the corresponding part of the dorsal. The length of the first 

 spine nearly equals that of the first dorsal one (-5), and the second is twice as 

 long (-11). 



The caudal fin is emarginated and its lobes rounded ; its median rays form 

 18 of the total length and are a quarter less than the longest (-25). The pec- 

 torals are rounded at the angles and equal in length "22 of the total. The 

 ventral fins are inserted a little behind the bases of the pectorals. The spine 

 equals the second anal (-11) and is half as long as the first and longest ray 

 (=22) and equal to the internal (-11). 



The scales are arranged at the region of greatest height in fifteen rows( ) 

 and on the caudal peduncle in seven / \. There are twenty-six obliquely 



transverse rows, and twenty-one are perforated for the upper part of the lateral 

 line. The scales of the cheeks are in three rows. 

 The formula for the fins and scales are as follows : 



D. XIII. 12. A. II. 12. C. 5. I. 7. 6. I. 4. P. I. 1. 17. V. I. 5. Scales 

 4 3 



2526 L. 1. sap. 2021. 



10 3 



[March, 



