NATURAL SCIENCES OF PHILADELPHIA. 135 



Hemichromis aukitos Gill. 



The body is oblong and arched from the iuterorbital region to the end of the 

 dorsal, both of which are at the same horizon ; the height is greatest under 

 the seventh dorsal spine where it nearly equals three-tenths ( - 29) of the 

 length; behind the dorsal fin, it exceeds an eighth ("13), and at the lowest 

 part nearly equals a ninth ("11) of the length. The greatest thickness is nearly 

 equal to a seventh of the length. 



The head forms three-tenths ( - 30) of the total length ; its height at the pre- 

 opercular margin bears a proportion to the same length of 23-100, and at the 

 pupil of 18-100. The profile above is perfectly rectilinear, and little oblique 

 along the intermaxillary groove, from the region above the pupil to the sym- 

 phisis of the jaw. The snout is acutely conical and nearly equals a third of 

 the head's length (9-100 of total.) The preorbital bone is highest behind, 

 and exceeds half the diameter of the eye, while between that point and the 

 nostrils it equals the same half. The preoperculum is vertical behind, slightly 

 prominent at its angle and obliquely curved forwards. The operculum forms 

 less than a third (9-30) of the head's length, and its angle is rounded. The 

 subopercular border behind is nearly vertical, and has a shallow emargination, 

 while below it is very obliquely rounded ; the height of the operculum and 

 suboperculum combined exceeds half (16-30) of the head's length. The iu- 

 terorbital region is flattened, and the sinus for the pedicles of the intermax- 

 illary bones is indicated by a semielliptical outline, terminating at the vertical 

 of the front border of the pupil. 



The teeth are tipped with brown and in a regular row in each jaw, about 

 twenty-five on each side in the upper (25 I. I. 25), and sixteen in the lower 

 16(-3, 4-)16 ; the two front teeth of the upper are two or three times as long as 

 the others, and that on each side is also rather larger than the others. The 

 three or four teeth on each at the front are somewhat larger and separated 

 from the others. The second series of small teeth, which are also tipped with 

 brown, is separated by a wide interval in front, but gradually approaches the 

 outer row towards the side. 



The dorsal fin commences over the end of the operculum ; its base is one 

 and a half times longer than the head (44^ of length) ; the spinous portion 

 exceeds the head's length ('31), and the soft is considerably less than half as 

 long (*13^). The spines rapidly and regularly increase in a curved line from 

 the first to the fifth, and behind the latter very slowly increase towards the 

 last ; the first spine nearly equals the lesser height of the preorbital bone ( '3j), 

 and is much less than half as long as the fifth ("8) and less than a third as 

 long as the last one ( - 11). The soft portion is acuminated at the middle or 

 sixth ray, which exceeds by half the length of the longest spine as well as 

 the last ray. 



The anal fin commences under the third ray of the dorsal fin, and ends under 

 or nearly under or slightly behind its last ; its base exceeds an eighth ("12) 

 of the total length ; the three spines regularly increase ('4; *7; '9) towards 

 the soft part ; the latter is acuminated like the dorsal, its longest ray equal- 

 ling that of the dorsal ("16), and twice the length of its last ray (-8). 



The caudal fin, when expanded, is almost truncated, the median rays form- 

 ing almost a fifth (*19), and the longest quite equalling a fifth ("20) of the 

 total length. 



The pectoral fins are slender and equal the longest dorsal and anal rays (*16). 

 The ventral fins are immediately behind the vertical of the lower axillae of the 

 pectorals. The spine equals a third ('10) of the head's length, and is as long 

 as the fifth ray; the first ray is simply bifurcated, and equals - 23 of the total 

 length ; the other rays doubly or triply subdivided. 



The scales are nearly equal, except on the abdomen, where they are much 

 smaller. There are twenty-five oblique rows, and at its deepest portion thir- 

 teen longitudinal rows, three of which are above and nine below the lateral 



1862.] 



