294 THE ARCTURUS ADVENTURE 



classify the tail as a recognition mark, a feature 

 so characteristic of gregarious animals, and the 

 lateral parti-colored band may, as likely as not, 

 have served the purpose of a warning signal to 

 any who may have instinctive appreciation of the 

 danger which it advertised. 



The gill openings were enormously elongated, 

 perhaps as an aid in permitting a strong in-and- 

 out-rush of water, when this was roiled by floating 

 detritus from the continual gnawing. Just back 

 of the gills were the pectoral fins, long, with a hint 

 of falcateness, and properly strong to govern the 

 myriad adjustments of every day's activity. When 

 balanced close alongside a rock, the pectorals were 

 used alternately to fend off with, in addition to 

 their more usual functions of balancing and pro- 

 pulsion. They are wonderfully strutted, hinged 

 on an oblique base, which constitutes the cross-bar 

 of the A formed by the clavicle and post-clavicle. 

 The superficial muscle which leads straight for- 

 ward from this fin, controls the posterior half of 

 the pectoral rays, and, when it contracts, curves 

 them around and out, until they form a most sym- 

 metrical, forwardly directed trough or cup — which 

 in its function of a brake or backing organ, is of 

 more importance than the backward push of a 

 swifter fish. 



Below the pectoral and slightly to the rear, 

 the ventral fins arose, close together, on the profile 

 of the chest. They were fronted by very stout, 

 rough spines, and the chest directly in front was 

 quite broad and flat. A number of times I saw 



