168 Z. M. Lambe — Fish Fauna of the Albert Shales. 



in length, about equal to the maximum depth of the body. 

 Eye of moderate size, placed far forward. Fins well-developed. 

 Dorsal fin beginning a little behind the mid-length of the fish, 

 triangular, about the same size as, and arising somewhat in 

 advance of, the anal fin. Caudal fin much prolonged in upper 

 lobe, deeply forked. Pectoral fins large, w T ith a short base. 

 Pelvic pair if anything nearer to the anal fin than to the 

 pectorals, of small size. Teeth minute. Suspensorium oblique. 



Anterior flank scales, figures 1 and 2, about as deep as long 

 (exposed surface), ornamented with striations, of which about 

 six are fine and parallel to the lower and anterior margins, 

 whilst three or four are coarse and have an oblique backward 

 and downward direction in the upper posterior quarter of the 

 scale. Posterior margin of scales serrated. Posterior flank 

 scales with fewer oblique striae, the remainder of the exposed 

 surface being smooth ; posterior margin with fewer but rela- 

 tively coarser serrations. Scales of body prolongation of tail 

 diamond-shaped. 



Enlarged ridge scales present from near the head to the dor- 

 sal fin, and from behind that fin on to and along the upper 

 lobe of the tail. There are also about three similarly enlarged 

 scales in advance of the anal fin, and about the same number 

 between it and the caudal. The enlarged scales are coarsely 

 and irregularly striated longitudinally, longer than broad, nar- 

 rowly rounded in front and somewhat pointed behind. Fin 

 rays jointed throughout, except the principal anterior ones of 

 the pectoral fins, which appear to be entire proximally. They 

 subdivide distally and have the appearance of being slightly 

 striated in the direction of their length. Minute fulcra are 

 present on the margin of the lower caudal lobe and on the 

 anterior margins of the other fins. The head bones are 

 ornamented with longitudinal ridges and tubercles, and tran- 

 sitions between the two. 



The scales of the type specimen of H. cairnsi are well pre- 

 served with the sculpture particularly definite. The specimen 

 itself is rather larger than the average sized specimens of R. 

 alberti. To the writer the striation of the scales appears to 

 be the same in both species, poorly preserved in the type of 

 J2. alberti but very clearly shown in the type of jR. cairnsi, 

 with a like serration of the posterior margin in both. Other 

 characters distinguishing the two species are not observed and 

 the conclusion has been reached that there is no real distinction 

 between the two. 



