82 BULLETIN OF THE 



nasals bend out toward the rostral, without approaching closely, then pass for- 

 ward and end blindly near the tip, at a considerable distance apart. Above 

 the front edge of the mouth the subrostral meets the nasal in a sharp angle. 

 The nasal curve is comparatively slight. Traces of an oral were not detected. 



Excessive thinness of the skin, by bringing the canals so close to the sur- 

 face, favors the presence of furrows rather than tubes, or, to go still further, 

 leads to the disappearance of the canals altogether, as in case of the orals of 

 this and other species. 



Characteristic features of the system on this shark are the isolation of the 

 prenasal, the length of the orbito-nasal, the suppression of the suborbital, the 

 direction of the orbital, the bisection of the rostral, the division of the aural, 

 and the open lateral tubes. Several points, in occipitals, cranials, orbitals, and 

 orbito-nasals, recall similar ones in Chlamydoselachus; the latter, however, is 

 widely withdrawn by consideration of its lack of division in aural and rostrals, 

 the position of its prenasal, and its possession of oral, gular, and spiracular 

 canals. 



H. pectorosus is, in most particulars, similar to H. maculatus. Its laterals 

 end about two fifths of the length of the tail in advance of the extrem- 

 ity, making a decided and broad curve downward to the fibrous part of the 

 caudal. 



A specimen of H. cinereus has closed corporal canals, or tubes, of similar 

 position and outline as the two species of this genus already noticed, but 

 reaching a little farther toward the caudal notch than in H. pectorosus. 



Chlamydoselachus. 



Chlamydoselachus anguineus (Plate XV.) has the laterals open throughout 

 their whole extent, with the exception of less than an inch immediately be- 

 hind the aural. From each edge enlarged scales overhang the groove, enclos- 

 ing it in a measure and protecting it. Along the flanks the canals are nearly 

 straight. The caudal curve is very gradual in one specimen, more abrupt in 

 another, and on one side of the second descends, then rises to repeat the curve. 

 On the body, the canal lies a little above the crease between the muscles of 

 the back and those of the flank. On the tail, its track lies a little below the 

 middle of the muscular portion ; it continues thus, with a few slight breaks 

 posteriorly, to within an inch of the end of the vertebral column, where it 

 stops. 



In the sketch the courses of the closed cephalic tubes are indicated by lines 

 of dots, each of the larger of which marks tbe opening of one of the short 

 tubules. The aural is closed. It has no tubules. Contrary to what obtains 

 in other Galei, it lies in front of the so-called ear openings. These openings, 

 however, are at the ends of tubes the inner extremities of which are in front 

 of the canal. The canal is nearly straight, bending slightly forward in the 

 middle and a little backward near each end. The occipitals are long and 



