44 DEEP SEA FISHES. 



that the text was not improved by the transformation at the same time that 

 it was made to appear as if original with these authors. 



Lateral System. In the worlv on tlie Lateral System published in the Bul- 

 letin of the Museum of Comparative Zoology, vol. XVII., 1888, p. 57, the 

 cephalic canals of Chlamydoselachus were traced from the openings on the 

 surface of the skin. Whether the diagram thus obtained agreed accurately 

 with the course of the tubes within could only be determined by dissection, 

 which was accomplished later and the results are given on Plate LXX. It 

 will be seen that in the two cases the diagrams are in close agreement. 

 The most peculiar features of the system in the genus appear in the pres- 

 ence of gular {(/) and spiracular {sp) canals, in the transverse median (;m), and 

 in the tranverse prenasals {jm) parallel with the nasals (ii) for some distance 

 at each side of the median. On individuals there is a manifest tendency to 

 irregularity in the lateral canal just above the forward end of the caudal ; 

 on one specimen the line on the right side makes a sharp curve down at this 

 point, then takes a straight course backward, but on the left side the line turns 

 down, then up, and then down again, making a sinuous line for about an inch 

 and a half before continuing straight back. Transverse median [m] tubes 

 are not rare among the other selachia, as will be seen by reference to Prio- 

 nodon, Alopias, Rhinobatus, Eaia, Myliobatis, Rhinoptera, and Dicerobatis 

 (Lat. Syst., Plates YL, XII., XXIV., XXV., XXIX., XLIX., LI., LIIL). 



If Isistius and Centroscyllium are compared with this genus, Plates LXIX. 

 and LXX. of the present work, gular and spiracular tubes are seen to be 

 absent in the first two, and the median is longitudinal, the nasals are trans- 

 verse, while the prenasals are continuations of the rostrals on the top of the 

 snout. The connections of orbital [orli) with suborbital or orbitonasal {on) 

 and angular {anrj) are the same in each of the three cases. Whether the 

 gular and the spiracular tubes of Chlamydoselachus are to be regarded as 

 primitive features derived from a remote ancestry or whether they are more 

 recent differentiations is yet undetermined, but perhaps the better conclu- 

 sion is that they have accompanied the peculiar branchial structure from 

 some of the earliest of the sharks. 



