74 BULLETIN OF THE 



peculiarly scalloped appearance, caused by the rising of short sections of the 

 edges as prominent rounded flanges supported by ribbed cartilaginous expan- 

 sions. At the end of each pair of these flanges the walls are lower, which 

 gives an appearance of rounded holes into the grooves. Between the holes the 

 edges are somewhat zigzag. 



On the scapular region the lateral (7) makes a moderate curve upward ; on 

 the flank it is slightly sinuous ; and on the anterior portion of the tail, near 

 the forward end of the lower lobe of the caudal fin, it descends to the lower 

 edge of the muscles, a position retained to the extremity. In its middle the 

 aural (au) is bent back, forming an angle from which a short post-aural branch 

 reaches toward the dorsal spine ; the canal crosses behind the aqueducts. 

 Aural and cranial (cr) are joined ; they are connected with lateral and orbital 

 (orb) by an occipital (oc) of moderate length passing downward and backward. 

 The cranials converge to some extent on the forehead ; on each side of the 

 frontal holder they turn out a little, but approach again on the snout. Below 

 the posterior border of the orbit the orbital meets the jugular (j) and the sub- 

 orbital (so). From this point the suborbital passes forward to join the ros- 

 tral (r) at the end of the snout, rising well up in front of the eye in an open 

 loop, somewhat inclined forward. An individual variation appears in each of 

 two specimens at hand : in one the angular (ang) unites with the jugular, in 

 the other with the suborbital. At first the angular passes downward to the 

 oral (o); thence it goes forward to the nasal (n) and the subrostral (sr). The 

 jugular runs obliquely backward and continues across the throat in a broken 

 line. Beneath the back part of the eye the oral leaves the angular, and may 

 be traced across the chin in a series of dashes or dots. The nasal lies in front 

 of the nostril ; it bends forward and meets its fellow in advance of the nares, 

 but forms neither median nor prenasals. From the suborbitals the subrostrals 

 extend toward each other and unite in a median ; a short distance posteriorly 

 they diverge to meet the angulars. The second specimen differs from that just 

 noted in having the angular united with the suborbital, and the jugular less 

 noticeable on the throat. The first of these features is an approach to the 

 condition in Callorhynchus, where angular, oral, and jugular connect with the 

 suborbital, but not with each other. 



Callorhynchus. 



Callorhynchus antardicus (Plates III., IV.) differs from Chimsera, and agrees 

 with the majority of the Sharks, in possessing canals that are tubes, instead of 

 furrows. On the flank the lateral rises a little in the scapular region ; thence 

 it is sinuous to the end of the dorsal; and thence straight to a point above the 

 lower lobe of the caudal fin, where it makes an abrupt downward bend to the 

 lower edge of the muscles, which position it retains to the end. 



In the middle the aural is much turned back; but it forms no angle and 

 sends off no branch. Forward from the aural the cranials are gradually con- 



