1258 DR. ERIK A. STENSIO : NOTES 



commissure, and it is also conceivable that its anterior parts 

 anastomosed with the anterior end of the supraorbital canal as 

 pointed out above, but it is not distinctly preserved anterior of 

 the orbit in my specimens. 



In the jugal there issues from the infraorbital canal a jugal 

 canal (jx, text-fig. 4), which runs backwards and downwards to 

 the squamosal, in which it continues to the postero-ventral 

 corner. In its further course this canal must have entered the 

 quadratojugal, if the restoration of this bone given by Bryant is 

 correct. As the most postero-ventival part of the canal seems to 

 be homologous with a ventral part of the preopercular canal (c/. 

 Stensio, 1921, pp. 76-77), the quadral.ojugal ought to comprise a 

 preopercular component (cf. Pearson, 1922, pp. 56-58). 



A true preopercular canal is not developed. The mandibular 

 canal is not clearl}^ seen in any specimens. 



The cephalic portion of the main lateral line {Ic, text-fig. 4) 

 has its anterior end at the boundary between the supratempoi-al 

 and intertemporal, where it is directly continuous with the 

 posterior end of the infraorbital canal. It runs backward 

 through the supratemporal and the lateral one of the three extra- 

 scapular bones. Through a well- developed supratemporal 

 commissure (s.coni., text-fig. 4), which pierces the three extra- 

 scapular bones transversel}^ it is in communication with that of 

 the opposite side. 



On the posterior part of the dorsal surface of the frontal there 

 is found a transverse fine groove (mp, text-fig. 4), which continues 

 laterally also over an adjacent part of the supratemporal. 

 Another groove (pp, text-fig. 4), which, however, is very short, 

 issues from the medial end of the former in a postero-lateral 

 direction. The two grooves which are described by Bryant as 

 a sensory canal proper (p. 12) and which, as it seems, have been 

 interpreted in this way also by Watson (1921, p. 334), are 

 undoubtedly developed for lines of pit organs. The longer of 

 tliem probably lodges the middle head line of these organs, and 

 the short obliquely running one the posterior head line {cf. 

 Stensio. 1921, pp. 218, 263 ; 1922 a, pp. 224, 235 ; 1922 b : cf. also 

 Allis, 1899, pp. 502-509; 1900, p. 445; 1903, p. 187; 1905, 

 pp. 406, 410, 418, 440, 452, 465, 469, 474, 484 : Herrick, 1901, 

 pp. 222-223, pi. xiv. : Pander, 1860, taf. iii. figs. 1, 3, 4, 12, 13, 

 23 ; taf. iv. fig. 2 : Jaekel, 1911, figs. 84, 85). I find no certain 

 traces of any anterior head line. 



Of the other structures described as sensory canals by Bryant, 

 the postei-ior one of the two on the mandibula is clearly shown in 

 my specimen to be a pit line, and the same ought also to be the 

 case with the other ones shown in his restorations (Bryant's 

 text-figs. 2 c, 3 6). 



As is evident from this description, the sensor}^ canals proper 

 of Eusthenopteron are developed exactly as described by Goodrich 

 in Osteolepis (Goodrich, 1919) and by me in DictyonosteAis and 



