MUSEUM OF COMPARATIVE ZOOLOGY. 107 



site the angle of the mouth three or four tubules are sent downward and for- 

 ward toward the lower border of the cephalic fin; a couple are sent inward 

 behind the mouth; and several short ones are extended inward just before 

 the tube enters its outward course along the border of the pectoral. Toward 

 the anterior margin of this fin the canal puts forth a large number of short 

 tubules, and near the outer angle, at the point of turning back on itself, two 

 elongate branches are extended toward the tip. Each of these branches bears 

 tubules. Retuniiiig toward the mouth the course of the pleiu'al is not much 

 farther from the edge. At first after making the bend it sends several tubules 

 forward, then, near the middle of the fin, a number turn backward; nearing the 

 first gill opening, some start forward, but turn and cross the canal, and still 

 nearer, before turning back by the side of the extension of the angular, a few 

 irregular branches are pushed forward. In their backward track the two inner 

 sections of these sub-pleurals lie close together. The outer of the two has by 

 fiir the greater number of tubules; from the shoulder girdle, anteriorly it sends 

 these outward; near the girdle they are turned inward to cross the inner tube 

 and reach the abdominal region. Opposite the middle of the abdomen, near the 

 end of the course, the majority of the branches turn out and backward; a few 

 only turn in to cross the tube; and at the turning-point of the tube an elon- 

 gate tubule goes back upon the ventral fin. As the canal goes forward toward 

 the jugular, it bears. several branches turning toward the ventral region, then 

 a few that cross the other section of the tube outward; but after leaving a point 

 opposite the middle of the belly, it bears no others. 



Aural. — This tube is elongate and strongly bent back in its middle, behind 

 the openings of the aqueducts. Near the median line it sends back three or 

 four tubules. 



Occipitals. — From the aural, each of these tubes extends toward the eye, at 

 the same time making a broad curve toward the branchial area, and sending 

 several irregular branches in the same direction. 



Cranials. — A cranial goes forward from the end of each occipital directly 

 toward the tip of the outstretched cephalic fin, without passing beyond the 

 skull. Posteriorly each bears a number of tubules reaching toward the median 

 line, but beyond a third of the distance forward they all reach outward to the 

 supraciliary prominence, where the}' end in a band of thickly set punctures. 

 Anteriorly the tubules are more numerous, more slender, and more crowded. 



Bostrals. — The rostral turns rather abruptly back and inward from the end 

 of the cranial. It runs near the front edge of the snout until about half-way 

 to the median line, where it passes to the lower surface. On the under side 

 of the snout it curves broadly in the direction of the prenasals, then, taking a 

 lateral direction before reaching the mouth, crossing and recrossing the nasal, 

 and making a bend forward in front of the nostril, it crosses the pleural before 

 meeting the orbito-nasal, which it joins opposite the corner of the mouth. One 

 of the rostrals (sr), that on the right side of the specimen dissected, appears 

 to be abnormal; it crosses the pleural, and a short distance behind it stops 

 abruptly, making no connection whatever. 



