1887.] ON THE LATERAL LINE OF SQUALORAJA. 481 



information as to the perishable tissues originally associated with 

 the skeletal fragments he finds in the rocks ; and such is all the 

 more to be regretted in the present instance, since the Pteraspidian 

 fishes are the earliest undoubted members of the class that have 

 hitherto been recognized in geological history. 



3. Note on the " lateral Line " of Sqiialoraja. 

 By A. Smith Woodward, F.Z.S. 



[Eeceived April 28, 1887.] 



In my description of the fossil Liassic Selachian Squaloraja, 

 read before this Society in October last (see P. Z. S, 1886, p. 527), 

 some series of very minute dermal ringlets are noted in the cephalic 

 and caudal regions, and these are regarded as designed for the 

 strengthening of the edges of those flattened parts of the body. 

 They are marked by the letter d adjoining the rostral cartilages in 

 fig. 1, j)l. Iv. loc. cit., and are also shovt-n in connected series along 

 the tail, parallel to an irregular dermal ridge which is similarly 

 designated. They are, moreover, seen in the original of fi;;. 3, and 

 in the caudal region of the specimen previously figured by Davies. 



Subsequent studies have led me to determine that these curious 

 structures are truly the supports of the canal of the "lateral line." 

 In the living Chimera, the open groove in which the sense-organs 

 are lodged is strengthened throughout by precisely similar rings, 

 as originally observed by Stannius ' and Leydig ^, and figured and 

 described by the latter; and von Meyer ^ has likewise discovered 

 these calcifications in a closely-allied fossil form from the Upper 

 Jurassic of Bavaria. They have been aptly compared with the 

 tracheal rings of some small air-breathing vertebrate. Their 

 remains upon the tail show that they were incomplete, exactly as in 

 the existing genus just mentioned ; and we may therefore conclude 

 that Squaloraja was characterized by an open sensory canal of the 

 essential Chimaeroid type. The circumstance adds one more to the 

 series of points in which the old Selachian seems to be related to 

 the last-named order, and it is thus particularly worthy of note. 



' H. Stannius, Lebrb. vergl. Anat Wirbeltbiere, 1846, p. 49. 



^ P. Leydig, " Zur Anatoniie und Histologie der Chimcera monstrosa" Miiller's 

 Arcbiv, 1851, p. 2,51, pi. x. flg. 2. 



2 H. von Meyer, " Chimera (Ganodus) avita, aus dem lithographiscben 

 Schiefer von Eicbstiitt," Pala3ontograpbica, vol. x. (1862), p. 92, pi. xii. 



